CUB-128: Build Settings page

frontend/src/App.tsx

@@ -1,7 +1,8 @@
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
-import { BrowserRouter, Routes, Route } from 'react-router-dom'
+import { BrowserRouter, Routes, Route, NavLink } from 'react-router-dom'
+import { Package, Settings } from 'lucide-react'
 import InventoryPage from './pages/InventoryPage'
-import FilamentDetailPage from './pages/FilamentDetailPage'
+import SettingsPage from './pages/SettingsPage'
 
 const queryClient = new QueryClient()
 
@@ -10,14 +11,43 @@ export default function App() {
     <QueryClientProvider client={queryClient}>
       <BrowserRouter>
         <div className="min-h-screen bg-slate-900 text-slate-50">
-          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
+          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-4 sticky top-0 z-20">
+            <div className="flex items-center gap-3 mr-4">
               <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
               <h1 className="text-lg font-semibold">Extrudex</h1>
+            </div>
+            <nav className="flex items-center gap-1">
+              <NavLink
+                to="/"
+                end
+                className={({ isActive }) =>
+                  `inline-flex items-center gap-1.5 rounded-md px-3 py-1.5 text-sm font-medium transition-colors ${
+                    isActive
+                      ? 'bg-emerald-600/20 text-emerald-400'
+                      : 'text-slate-400 hover:text-slate-200 hover:bg-slate-700'
+                  }`
+                }
+              >
+                <Package size={15} /> Inventory
+              </NavLink>
+              <NavLink
+                to="/settings"
+                className={({ isActive }) =>
+                  `inline-flex items-center gap-1.5 rounded-md px-3 py-1.5 text-sm font-medium transition-colors ${
+                    isActive
+                      ? 'bg-emerald-600/20 text-emerald-400'
+                      : 'text-slate-400 hover:text-slate-200 hover:bg-slate-700'
+                  }`
+                }
+              >
+                <Settings size={15} /> Settings
+              </NavLink>
+            </nav>
           </header>
           <main className="p-4">
             <Routes>
               <Route path="/" element={<InventoryPage />} />
-              <Route path="/filament/:id" element={<FilamentDetailPage />} />
+              <Route path="/settings" element={<SettingsPage />} />
             </Routes>
           </main>
         </div>

frontend/src/pages/FilamentDetailPage.tsx

@@ -1,391 +0,0 @@
-import { useState } from 'react'
-import { useParams, useNavigate } from 'react-router-dom'
-import { useQuery, useQueryClient } from '@tanstack/react-query'
-import { ArrowLeft, Pencil, Trash2, AlertTriangle, Loader2, Archive } from 'lucide-react'
-import ColorSwatch from '../components/ColorSwatch'
-import { fetchFilamentById, fetchUsageLogs, deleteFilament } from '../services/filamentService'
-import type { UsageLog } from '../types/filament'
-
-export default function FilamentDetailPage() {
-  const { id } = useParams<{ id: string }>()
-  const spoolId = Number(id)
-  const navigate = useNavigate()
-  const queryClient = useQueryClient()
-  const [deleteConfirm, setDeleteConfirm] = useState(false)
-  const [deleting, setDeleting] = useState(false)
-
-  const {
-    data: spool,
-    isLoading: spoolLoading,
-    error: spoolError,
-    refetch: refetchSpool,
-  } = useQuery({
-    queryKey: ['filament', spoolId],
-    queryFn: () => fetchFilamentById(spoolId),
-    enabled: !isNaN(spoolId),
-  })
-
-  const {
-    data: usageLogs,
-    isLoading: usageLoading,
-    error: usageError,
-    refetch: refetchUsage,
-  } = useQuery({
-    queryKey: ['usage-logs', spoolId],
-    queryFn: () => fetchUsageLogs(spoolId),
-    enabled: !isNaN(spoolId),
-  })
-
-  const handleDelete = async () => {
-    setDeleting(true)
-    try {
-      await deleteFilament(spoolId)
-      queryClient.invalidateQueries({ queryKey: ['filaments'] })
-      navigate('/')
-    } catch {
-      setDeleting(false)
-      setDeleteConfirm(false)
-    }
-  }
-
-  // ── Loading state ──
-  if (spoolLoading) {
-    return (
-      <div className="flex flex-col items-center justify-center py-24 gap-3 text-slate-400">
-        <Loader2 size={32} className="animate-spin text-emerald-400" />
-        <span>Loading spool details…</span>
-      </div>
-    )
-  }
-
-  // ── Error state ──
-  if (spoolError || !spool) {
-    return (
-      <div className="flex flex-col items-center justify-center py-24 gap-4">
-        <div className="flex h-14 w-14 items-center justify-center rounded-full bg-red-900/30">
-          <AlertTriangle size={28} className="text-red-400" />
-        </div>
-        <p className="text-red-400 font-medium">Failed to load spool details.</p>
-        <div className="flex gap-3">
-          <button
-            onClick={() => refetchSpool()}
-            className="rounded-lg bg-slate-700 px-4 py-2 text-sm font-medium text-slate-200 hover:bg-slate-600 transition-colors"
-          >
-            Retry
-          </button>
-          <button
-            onClick={() => navigate('/')}
-            className="rounded-lg bg-slate-800 border border-slate-700 px-4 py-2 text-sm font-medium text-slate-300 hover:bg-slate-700 transition-colors"
-          >
-            Back to Inventory
-          </button>
-        </div>
-      </div>
-    )
-  }
-
-  const pctRemaining = spool.initial_grams > 0
-    ? (spool.remaining_grams / spool.initial_grams) * 100
-    : 0
-  const isLow = spool.remaining_grams <= (spool.low_stock_threshold_grams || 0)
-
-  return (
-    <div className="space-y-6">
-      {/* ── Header Bar ── */}
-      <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
-        <button
-          onClick={() => navigate('/')}
-          className="inline-flex items-center gap-2 rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm font-medium text-slate-200 hover:bg-slate-700 active:bg-slate-600 transition-colors w-fit"
-        >
-          <ArrowLeft size={16} />
-          Back to Inventory
-        </button>
-
-        <div className="flex items-center gap-2">
-          <button className="inline-flex items-center gap-2 rounded-lg bg-slate-700 px-4 py-2 text-sm font-semibold text-slate-200 hover:bg-slate-600 active:bg-slate-500 transition-colors">
-            <Pencil size={16} />
-            Edit
-          </button>
-          <button
-            onClick={() => setDeleteConfirm(true)}
-            className="inline-flex items-center gap-2 rounded-lg bg-red-900/30 border border-red-700 px-4 py-2 text-sm font-semibold text-red-300 hover:bg-red-900/50 active:bg-red-900/70 transition-colors"
-          >
-            <Trash2 size={16} />
-            Delete
-          </button>
-        </div>
-      </div>
-
-      {/* ── Spool Info Card ── */}
-      <div className="rounded-xl border border-slate-700 bg-slate-800 overflow-hidden">
-        {/* Card header */}
-        <div className="px-6 py-5 border-b border-slate-700 flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
-          <div className="flex items-center gap-3">
-            <ColorSwatch colorHex={spool.color_hex} size={36} />
-            <div>
-              <h1 className="text-xl font-bold text-slate-100">{spool.name}</h1>
-              <p className="text-sm text-slate-400">
-                {spool.brand && <span>{spool.brand} · </span>}
-                {spool.diameter_mm}mm
-              </p>
-            </div>
-          </div>
-          <div>
-            {isLow ? (
-              <span className="inline-flex items-center gap-1.5 rounded-full bg-red-900/40 border border-red-700 px-3 py-1 text-sm font-medium text-red-300">
-                <AlertTriangle size={14} /> Low Stock
-              </span>
-            ) : (
-              <span className="inline-flex items-center gap-1.5 rounded-full bg-emerald-900/30 border border-emerald-700 px-3 py-1 text-sm font-medium text-emerald-300">
-                In Stock
-              </span>
-            )}
-          </div>
-        </div>
-
-        {/* Card body — 2-column grid */}
-        <div className="px-6 py-5 grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-x-8 gap-y-4">
-          <DetailItem label="Material" value={spool.material_base?.name ?? '—'} />
-          <DetailItem label="Finish" value={spool.material_finish?.name ?? '—'} />
-          <DetailItem
-            label="Modifier"
-            value={spool.material_modifier?.name ?? 'None'}
-          />
-          <DetailItem label="Color" value={spool.color_hex.toUpperCase()} />
-          <DetailItem label="Brand" value={spool.brand || '—'} />
-          <DetailItem label="Diameter" value={`${spool.diameter_mm}mm`} />
-          <DetailItem
-            label="Remaining"
-            value={
-              <span className="font-semibold tabular-nums">
-                {spool.remaining_grams.toLocaleString()} g
-              </span>
-            }
-          />
-          <DetailItem
-            label="Initial"
-            value={`${spool.initial_grams.toLocaleString()} g`}
-          />
-          <DetailItem
-            label="Cost"
-            value={
-              spool.cost_usd != null
-                ? `$${spool.cost_usd.toFixed(2)}`
-                : '—'
-            }
-          />
-        </div>
-
-        {/* Progress Bar */}
-        <div className="px-6 pb-5 pt-1">
-          <div className="flex items-center justify-between text-sm mb-1.5">
-            <span className="text-slate-400">
-              <span className="text-slate-200 font-semibold tabular-nums">
-                {spool.remaining_grams.toLocaleString()}g
-              </span>{' '}
-              of {spool.initial_grams.toLocaleString()}g
-            </span>
-            <span className="text-slate-400 font-medium tabular-nums">
-              {pctRemaining.toFixed(1)}%
-            </span>
-          </div>
-          <div className="w-full h-3 rounded-full bg-slate-700 overflow-hidden">
-            <div
-              className={`h-full rounded-full transition-all duration-500 ${
-                pctRemaining <= 10
-                  ? 'bg-red-500'
-                  : pctRemaining <= 25
-                    ? 'bg-amber-500'
-                    : 'bg-emerald-500'
-              }`}
-              style={{ width: `${Math.min(100, pctRemaining)}%` }}
-            />
-          </div>
-        </div>
-      </div>
-
-      {/* ── Usage History ── */}
-      <div className="rounded-xl border border-slate-700 bg-slate-800 overflow-hidden">
-        <div className="px-6 py-4 border-b border-slate-700">
-          <h2 className="text-lg font-semibold text-slate-100">Usage History</h2>
-        </div>
-
-        {/* Loading sub-state */}
-        {usageLoading && (
-          <div className="px-6 py-8 text-center text-slate-400">
-            <Loader2 size={20} className="animate-spin inline mr-2" />
-            Loading usage history…
-          </div>
-        )}
-
-        {/* Usage error sub-state */}
-        {usageError && !usageLoading && (
-          <div className="px-6 py-8 text-center">
-            <p className="text-red-400 text-sm">
-              Failed to load usage history.
-            </p>
-            <button
-              onClick={() => refetchUsage()}
-              className="mt-2 text-sm text-emerald-400 hover:text-emerald-300 underline"
-            >
-              Retry
-            </button>
-          </div>
-        )}
-
-        {/* Empty state */}
-        {!usageLoading && !usageError && usageLogs && usageLogs.length === 0 && (
-          <div className="px-6 py-10 text-center">
-            <Archive size={32} className="mx-auto text-slate-600 mb-2" />
-            <p className="text-slate-400 text-sm">No usage recorded yet.</p>
-            <p className="text-slate-500 text-xs mt-1">
-              Usage data will appear here when this spool is used in print jobs.
-            </p>
-          </div>
-        )}
-
-        {/* Table — desktop */}
-        {!usageLoading && !usageError && usageLogs && usageLogs.length > 0 && (
-          <>
-            <div className="hidden md:block overflow-x-auto">
-              <table className="w-full text-sm">
-                <thead className="bg-slate-800/50 text-slate-300">
-                  <tr>
-                    <th className="px-6 py-3 text-left font-semibold">Date</th>
-                    <th className="px-6 py-3 text-left font-semibold">Print Job</th>
-                    <th className="px-6 py-3 text-right font-semibold">mm Extruded</th>
-                    <th className="px-6 py-3 text-right font-semibold">Grams Used</th>
-                    <th className="px-6 py-3 text-right font-semibold">Cost</th>
-                  </tr>
-                </thead>
-                <tbody className="divide-y divide-slate-700">
-                  {usageLogs.map((log: UsageLog) => (
-                    <tr
-                      key={log.id}
-                      className="hover:bg-slate-700/30 transition-colors"
-                    >
-                      <td className="px-6 py-3 text-slate-200 tabular-nums">
-                        {new Date(log.logged_at).toLocaleDateString('en-US', {
-                          year: 'numeric',
-                          month: 'short',
-                          day: 'numeric',
-                        })}
-                      </td>
-                      <td className="px-6 py-3 text-slate-300">
-                        {log.print_job_name || `Job #${log.print_job_id ?? log.id}`}
-                      </td>
-                      <td className="px-6 py-3 text-right text-slate-200 tabular-nums">
-                        {log.mm_extruded.toLocaleString()}
-                      </td>
-                      <td className="px-6 py-3 text-right text-slate-200 tabular-nums">
-                        {log.grams_used.toFixed(2)} g
-                      </td>
-                      <td className="px-6 py-3 text-right text-slate-200 tabular-nums">
-                        {log.cost_usd != null ? `$${log.cost_usd.toFixed(3)}` : '—'}
-                      </td>
-                    </tr>
-                  ))}
-                </tbody>
-              </table>
-            </div>
-
-            {/* Mobile cards */}
-            <div className="md:hidden divide-y divide-slate-700">
-              {usageLogs.map((log: UsageLog) => (
-                <div key={log.id} className="px-4 py-4 space-y-2">
-                  <div className="flex items-center justify-between">
-                    <span className="text-sm font-medium text-slate-200">
-                      {log.print_job_name || `Job #${log.print_job_id ?? log.id}`}
-                    </span>
-                    <span className="text-xs text-slate-400 tabular-nums">
-                      {new Date(log.logged_at).toLocaleDateString('en-US', {
-                        month: 'short',
-                        day: 'numeric',
-                      })}
-                    </span>
-                  </div>
-                  <div className="flex items-center justify-between text-sm">
-                    <span className="text-slate-400">
-                      Extruded:{' '}
-                      <span className="text-slate-300 tabular-nums">
-                        {log.mm_extruded.toLocaleString()} mm
-                      </span>
-                    </span>
-                    <span className="text-slate-400">
-                      Used:{' '}
-                      <span className="text-slate-300 tabular-nums">
-                        {log.grams_used.toFixed(2)} g
-                      </span>
-                    </span>
-                    <span className="text-slate-400">
-                      {log.cost_usd != null ? (
-                        <>
-                          Cost:{' '}
-                          <span className="text-slate-300 tabular-nums">
-                            ${log.cost_usd.toFixed(3)}
-                          </span>
-                        </>
-                      ) : (
-                        '—'
-                      )}
-                    </span>
-                  </div>
-                </div>
-              ))}
-            </div>
-          </>
-        )}
-      </div>
-
-      {/* ── Delete Confirmation Modal ── */}
-      {deleteConfirm && (
-        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 backdrop-blur-sm p-4">
-          <div className="w-full max-w-sm rounded-xl bg-slate-800 border border-slate-700 p-6 shadow-2xl space-y-4">
-            <div className="flex items-center gap-3">
-              <div className="flex h-10 w-10 items-center justify-center rounded-full bg-red-900/30 flex-shrink-0">
-                <AlertTriangle size={20} className="text-red-400" />
-              </div>
-              <div>
-                <h3 className="text-lg font-semibold text-slate-100">
-                  Delete &ldquo;{spool.name}&rdquo;?
-                </h3>
-                <p className="text-sm text-slate-400">
-                  This permanently removes the spool and all usage history. This cannot be undone.
-                </p>
-              </div>
-            </div>
-            <div className="flex justify-end gap-3">
-              <button
-                onClick={() => setDeleteConfirm(false)}
-                disabled={deleting}
-                className="rounded-lg bg-slate-700 px-4 py-2 text-sm font-medium text-slate-200 hover:bg-slate-600 transition-colors disabled:opacity-50"
-              >
-                Cancel
-              </button>
-              <button
-                onClick={handleDelete}
-                disabled={deleting}
-                className="inline-flex items-center gap-2 rounded-lg bg-red-600 px-4 py-2 text-sm font-medium text-white hover:bg-red-500 transition-colors disabled:opacity-50"
-              >
-                {deleting && <Loader2 size={16} className="animate-spin" />}
-                {deleting ? 'Deleting…' : 'Delete'}
-              </button>
-            </div>
-          </div>
-        </div>
-      )}
-    </div>
-  )
-}
-
-/** Small detail row for the info card grid */
-function DetailItem({ label, value }: { label: string; value: React.ReactNode }) {
-  return (
-    <div>
-      <dt className="text-xs font-medium uppercase tracking-wider text-slate-500 mb-0.5">
-        {label}
-      </dt>
-      <dd className="text-sm text-slate-200">{value}</dd>
-    </div>
-  )
-}

frontend/src/pages/SettingsPage.tsx

@@ -0,0 +1,290 @@
+import { useState } from 'react'
+import { Save, Wifi, WifiOff, Sun, Moon, AlertCircle, CheckCircle2 } from 'lucide-react'
+
+// TODO: Replace with API calls to GET/PUT /api/settings once Dex implements the endpoint
+const DEFAULT_SETTINGS = {
+  lowStockThresholdGrams: 100,
+  filamentCrossSectionMm2: 2.405, // π × (0.875mm)² — standard 1.75mm filament
+  currency: 'USD',
+  theme: 'dark' as 'dark' | 'light' | 'system',
+}
+
+const CURRENCIES = ['USD', 'EUR', 'GBP', 'CAD', 'AUD', 'JPY']
+
+type ConnectionStatus = 'idle' | 'testing' | 'ok' | 'error'
+
+interface PrinterConfig {
+  name: string
+  type: 'bambu' | 'moonraker'
+  host: string
+}
+
+// TODO: Load from GET /api/printers once Dex implements the endpoint
+const MOCK_PRINTERS: PrinterConfig[] = [
+  { name: 'Bambu X1C #1', type: 'bambu', host: '192.168.1.100' },
+  { name: 'Bambu X1C #2', type: 'bambu', host: '192.168.1.101' },
+  { name: 'Voron 2.4 (Klipper)', type: 'moonraker', host: '192.168.1.200' },
+]
+
+function SettingRow({ label, hint, children }: { label: string; hint?: string; children: React.ReactNode }) {
+  return (
+    <div className="flex flex-col sm:flex-row sm:items-center gap-2 sm:gap-4 py-4 border-b border-slate-700 last:border-0">
+      <div className="sm:w-64 shrink-0">
+        <div className="text-sm font-medium text-slate-200">{label}</div>
+        {hint && <div className="text-xs text-slate-500 mt-0.5">{hint}</div>}
+      </div>
+      <div className="flex-1">{children}</div>
+    </div>
+  )
+}
+
+function SectionHeader({ title, description }: { title: string; description?: string }) {
+  return (
+    <div className="mb-2">
+      <h3 className="text-base font-semibold text-slate-100">{title}</h3>
+      {description && <p className="text-sm text-slate-400 mt-0.5">{description}</p>}
+    </div>
+  )
+}
+
+export default function SettingsPage() {
+  const [lowStockThreshold, setLowStockThreshold] = useState(DEFAULT_SETTINGS.lowStockThresholdGrams)
+  const [crossSection, setCrossSection] = useState(DEFAULT_SETTINGS.filamentCrossSectionMm2)
+  const [currency, setCurrency] = useState(DEFAULT_SETTINGS.currency)
+  const [theme, setTheme] = useState(DEFAULT_SETTINGS.theme)
+  const [saved, setSaved] = useState(false)
+  const [saveError, setSaveError] = useState(false)
+  const [printerStatus, setPrinterStatus] = useState<Record<string, ConnectionStatus>>({})
+
+  const [thresholdError, setThresholdError] = useState('')
+  const [crossSectionError, setCrossSectionError] = useState('')
+
+  const validate = () => {
+    let valid = true
+    if (!lowStockThreshold || lowStockThreshold < 0 || lowStockThreshold > 10000) {
+      setThresholdError('Must be between 0 and 10,000 g')
+      valid = false
+    } else {
+      setThresholdError('')
+    }
+    if (!crossSection || crossSection <= 0 || crossSection > 100) {
+      setCrossSectionError('Must be a positive number (typical: 2.405 for 1.75mm)')
+      valid = false
+    } else {
+      setCrossSectionError('')
+    }
+    return valid
+  }
+
+  const handleSave = async () => {
+    if (!validate()) return
+    try {
+      // TODO: PUT /api/settings with { low_stock_threshold_grams, filament_cross_section_mm2, currency, theme }
+      setSaved(true)
+      setSaveError(false)
+      setTimeout(() => setSaved(false), 3000)
+    } catch {
+      setSaveError(true)
+      setSaved(false)
+    }
+  }
+
+  const testPrinterConnection = async (printer: PrinterConfig) => {
+    setPrinterStatus(s => ({ ...s, [printer.host]: 'testing' }))
+    // TODO: POST /api/printers/test with { host, type } — Dex to implement
+    await new Promise(r => setTimeout(r, 1500))
+    // Mock: hosts ending in .100 or .200 pass, others fail
+    const ok = printer.host.endsWith('.100') || printer.host.endsWith('.200')
+    setPrinterStatus(s => ({ ...s, [printer.host]: ok ? 'ok' : 'error' }))
+  }
+
+  return (
+    <div className="space-y-6 max-w-2xl">
+      {/* Header */}
+      <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
+        <div>
+          <h2 className="text-xl font-bold text-slate-100">Settings</h2>
+          <p className="text-sm text-slate-400">App configuration for Extrudex</p>
+        </div>
+        <div className="flex items-center gap-3">
+          {saved && (
+            <span className="inline-flex items-center gap-1.5 text-sm text-emerald-400">
+              <CheckCircle2 size={16} /> Saved
+            </span>
+          )}
+          {saveError && (
+            <span className="inline-flex items-center gap-1.5 text-sm text-red-400">
+              <AlertCircle size={16} /> Save failed
+            </span>
+          )}
+          <button
+            onClick={handleSave}
+            className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-4 py-2 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors"
+          >
+            <Save size={16} /> Save Settings
+          </button>
+        </div>
+      </div>
+
+      {/* Inventory Settings */}
+      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
+        <SectionHeader
+          title="Inventory"
+          description="Controls how spools are tracked and displayed"
+        />
+        <SettingRow
+          label="Low stock threshold"
+          hint="Spools below this weight are flagged as low stock"
+        >
+          <div>
+            <div className="flex items-center gap-2">
+              <input
+                type="number"
+                min={0}
+                max={10000}
+                step={10}
+                value={lowStockThreshold}
+                onChange={e => setLowStockThreshold(Number(e.target.value))}
+                className={`w-32 rounded-lg bg-slate-800 border ${thresholdError ? 'border-red-500' : 'border-slate-700'} px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500`}
+              />
+              <span className="text-sm text-slate-400">grams</span>
+            </div>
+            {thresholdError && <p className="mt-1 text-xs text-red-400">{thresholdError}</p>}
+          </div>
+        </SettingRow>
+
+        <SettingRow
+          label="Filament cross-section area"
+          hint="Used to convert mm extruded → grams (π × r²)"
+        >
+          <div>
+            <div className="flex items-center gap-2">
+              <input
+                type="number"
+                min={0.01}
+                max={100}
+                step={0.001}
+                value={crossSection}
+                onChange={e => setCrossSection(Number(e.target.value))}
+                className={`w-36 rounded-lg bg-slate-800 border ${crossSectionError ? 'border-red-500' : 'border-slate-700'} px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500`}
+              />
+              <span className="text-sm text-slate-400">mm²</span>
+            </div>
+            {crossSectionError && <p className="mt-1 text-xs text-red-400">{crossSectionError}</p>}
+            <p className="mt-1 text-xs text-slate-500">1.75mm filament = 2.405 mm² · 2.85mm filament = 6.379 mm²</p>
+          </div>
+        </SettingRow>
+
+        <SettingRow label="Currency" hint="Used for cost display throughout the app">
+          <select
+            value={currency}
+            onChange={e => setCurrency(e.target.value)}
+            className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
+          >
+            {CURRENCIES.map(c => (
+              <option key={c} value={c}>{c}</option>
+            ))}
+          </select>
+        </SettingRow>
+      </div>
+
+      {/* Appearance */}
+      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
+        <SectionHeader title="Appearance" />
+        <SettingRow label="Theme" hint="Override system default color scheme">
+          <div className="flex items-center gap-2">
+            {(['system', 'dark', 'light'] as const).map(t => (
+              <button
+                key={t}
+                onClick={() => setTheme(t)}
+                className={`inline-flex items-center gap-1.5 rounded-lg px-3 py-2 text-sm font-medium border transition-colors ${
+                  theme === t
+                    ? 'bg-emerald-600 border-emerald-500 text-white'
+                    : 'bg-slate-800 border-slate-700 text-slate-300 hover:bg-slate-700'
+                }`}
+              >
+                {t === 'dark' && <Moon size={14} />}
+                {t === 'light' && <Sun size={14} />}
+                {t === 'system' && <span className="text-xs">Auto</span>}
+                {t !== 'system' && <span className="capitalize">{t}</span>}
+                {t === 'system' && <span>System</span>}
+              </button>
+            ))}
+          </div>
+        </SettingRow>
+      </div>
+
+      {/* Printer Connections */}
+      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
+        <SectionHeader
+          title="Printer Connections"
+          description="Test connectivity to configured printers"
+        />
+        {/* TODO: Load printer list from GET /api/printers */}
+        {MOCK_PRINTERS.map(printer => {
+          const status = printerStatus[printer.host] ?? 'idle'
+          return (
+            <SettingRow
+              key={printer.host}
+              label={printer.name}
+              hint={`${printer.type === 'bambu' ? 'Bambu MQTT' : 'Moonraker'} · ${printer.host}`}
+            >
+              <div className="flex items-center gap-3">
+                <StatusBadge status={status} />
+                <button
+                  onClick={() => testPrinterConnection(printer)}
+                  disabled={status === 'testing'}
+                  className="inline-flex items-center gap-1.5 rounded-lg bg-slate-700 border border-slate-600 px-3 py-1.5 text-xs font-medium text-slate-200 hover:bg-slate-600 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
+                >
+                  {status === 'testing' ? (
+                    <>
+                      <span className="animate-spin inline-block w-3 h-3 border border-slate-400 border-t-transparent rounded-full" />
+                      Testing…
+                    </>
+                  ) : (
+                    <>
+                      <Wifi size={12} /> Test Connection
+                    </>
+                  )}
+                </button>
+              </div>
+            </SettingRow>
+          )
+        })}
+      </div>
+
+      {/* Save footer (mobile convenience) */}
+      <div className="flex justify-end pb-4">
+        <button
+          onClick={handleSave}
+          className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-5 py-2.5 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors"
+        >
+          <Save size={16} /> Save Settings
+        </button>
+      </div>
+    </div>
+  )
+}
+
+function StatusBadge({ status }: { status: ConnectionStatus }) {
+  if (status === 'idle') return null
+  if (status === 'testing') {
+    return (
+      <span className="inline-flex items-center gap-1 rounded-full bg-slate-700 border border-slate-600 px-2 py-0.5 text-xs text-slate-300">
+        Testing…
+      </span>
+    )
+  }
+  if (status === 'ok') {
+    return (
+      <span className="inline-flex items-center gap-1 rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs text-emerald-300">
+        <CheckCircle2 size={11} /> Connected
+      </span>
+    )
+  }
+  return (
+    <span className="inline-flex items-center gap-1 rounded-full bg-red-900/30 border border-red-700 px-2 py-0.5 text-xs text-red-300">
+      <WifiOff size={11} /> Unreachable
+    </span>
+  )
+}

frontend/src/services/filamentService.ts

@@ -1,5 +1,5 @@
 import axios from 'axios'
-import type { FilamentSpool, ListResponse, UsageLog, FilamentFilter } from '../types/filament'
+import type { FilamentSpool, ListResponse, FilamentFilter } from '../types/filament'
 
 const API_BASE = '/api'
 
@@ -19,16 +19,6 @@ export async function fetchFilaments(filter: FilamentFilter): Promise<ListRespon
   return res.data
 }
 
-export async function fetchFilamentById(id: number): Promise<FilamentSpool> {
-  const res = await axios.get<FilamentSpool>(`${API_BASE}/filaments/${id}`)
-  return res.data
-}
-
-export async function fetchUsageLogs(spoolId: number): Promise<UsageLog[]> {
-  const res = await axios.get<UsageLog[]>(`${API_BASE}/usage-logs?spool_id=${spoolId}`)
-  return res.data
-}
-
 export async function deleteFilament(id: number): Promise<void> {
   await axios.delete(`${API_BASE}/filaments/${id}`)
 }

frontend/src/types/filament.ts

@@ -59,19 +59,6 @@ export interface ListResponse<T> {
   offset: number
 }
 
-export interface UsageLog {
-  id: number
-  spool_id: number
-  print_job_id?: number
-  print_job_name?: string
-  mm_extruded: number
-  grams_used: number
-  cost_usd?: number
-  logged_at: string
-  notes?: string
-  created_at: string
-}
-
 export interface FilamentFilter {
   material?: string
   finish?: string