feat(CUB-58): Agent Status SignalR Service (Angular)

- Scaffold Angular 17 frontend with standalone components
- Add @microsoft/signalr package dependency
- Create AgentStatusService connecting to /hub endpoint
  - Auto-reconnect with progressive delays
  - Listens for AgentStatusChanged and BroadcastMessage
  - Logs all updates to console
  - Exposes statusUpdates$ and connected$ observables
  - onStatusUpdate() alias matching CUB-58 spec
- Create AgentStatusUpdate interface (agentId, status, lastSeenAt)
- Add APP_INITIALIZER provider to start connection on app boot
- Register initializer in app.config.ts
- Update .gitignore for frontend build artifacts

frontend/tsconfig.json

@@ -0,0 +1,32 @@
+/* To learn more about this file see: https://angular.io/config/tsconfig. */
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "outDir": "./dist/out-tsc",
+    "strict": true,
+    "noImplicitOverride": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "sourceMap": true,
+    "declaration": false,
+    "experimentalDecorators": true,
+    "moduleResolution": "node",
+    "importHelpers": true,
+    "target": "ES2022",
+    "module": "ES2022",
+    "useDefineForClassFields": false,
+    "lib": [
+      "ES2022",
+      "dom"
+    ]
+  },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true,
+    "strictTemplates": true
+  }
+}