feat(frontend): safe-area insets + hardened reduced-motion

- Add viewport export with viewportFit: "cover" so iOS exposes
  env(safe-area-inset-*) (required for the insets to take effect).
- NavRail / TopBar / main / Toaster now respect safe-area insets so content
  clears the iPhone notch and home indicator in both portrait and landscape.
- prefers-reduced-motion: the media query already disabled declared animation
  classes; harden it with a global transition/animation duration override and
  kill the scan-line shimmer so motion-sensitive users get a fully static UI.

Verified tsc --noEmit + next build clean.

services/frontend/src/app/globals.css

@@ -262,6 +262,7 @@
 
 @media (prefers-reduced-motion: reduce) {
   .scan-line::after,
+  .scan-line,
   .animate-eq,
   .animate-spin-disc,
   .animate-pulse-ring,
@@ -269,5 +270,16 @@
   .animate-breathe {
     animation: none !important;
   }
+  .scan-line {
+    background: none !important;
+  }
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.001ms !important;
+    animation-iteration-count: 1 !important;
+    transition-duration: 0.001ms !important;
+    scroll-behavior: auto !important;
+  }
   html { scroll-behavior: auto; }
 }

services/frontend/src/app/layout.tsx

@@ -1,4 +1,4 @@
-import type { Metadata } from "next";
+import type { Metadata, Viewport } from "next";
 import { Bricolage_Grotesque, Inter, JetBrains_Mono } from "next/font/google";
 import { ThemeProvider } from "next-themes";
 import { Toaster } from "@/components/primitives/toast";
@@ -28,6 +28,13 @@ export const metadata: Metadata = {
     "AI-powered Discord moderation, voice monitoring, and media control console",
 };
 
+export const viewport: Viewport = {
+  themeColor: "#0a0a0c",
+  width: "device-width",
+  initialScale: 1,
+  viewportFit: "cover",
+};
+
 export default function RootLayout({
   children,
 }: Readonly<{