CUB-27: Responsive layout and adaptive navigation

frontend/src/app/layout/bottom-nav/bottom-nav.component.scss

@@ -1,7 +1,8 @@
 // ============================================================================
 // Bottom Navigation Bar — Mobile Navigation
-// Per spec Section 3.2: M3 NavigationBar pattern
-// Visible only on compact breakpoint (< 600px)
+// Per CUB-27 spec breakpoints:
+//   Compact (0–599px): Visible — M3 NavigationBar pattern
+//   Medium+ (≥600px): Hidden — nav rail takes over
 // ============================================================================
 
 .bottom-nav {
@@ -17,6 +18,8 @@
   align-items: center;
   justify-content: space-around;
   padding: 0 8px;
+  // Safe area inset for notched devices
+  padding-bottom: env(safe-area-inset-bottom, 0px);
 }
 
 .bottom-nav__item {
@@ -68,9 +71,24 @@
   white-space: nowrap;
 }
 
-// Show bottom nav only on compact breakpoint
+// ---------------------------------------------------------------------------
+// Compact (0–599px): Show bottom nav
+// ---------------------------------------------------------------------------
 @media (max-width: 599px) {
   .bottom-nav {
     display: flex;
   }
+}
+
+// ---------------------------------------------------------------------------
+// Medium+ (≥600px): Hidden — nav rail takes over
+// ---------------------------------------------------------------------------
+
+// ---------------------------------------------------------------------------
+// Accessibility: Reduced Motion
+// ---------------------------------------------------------------------------
+@media (prefers-reduced-motion: reduce) {
+  .bottom-nav__item {
+    transition: none;
+  }
 }