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/components/shell/nav-rail.tsx

@@ -40,7 +40,7 @@ export function NavRail() {
   const path = pathname ?? "/";
 
   return (
-    <nav className="glass m-3 mr-0 flex w-[68px] flex-col items-center gap-1 rounded-[18px] py-4">
+    <nav className="glass mb-[calc(0.75rem+env(safe-area-inset-bottom))] ml-[calc(0.75rem+env(safe-area-inset-left))] mt-[calc(0.75rem+env(safe-area-inset-top))] flex w-[68px] flex-col items-center gap-1 rounded-[18px] py-4">
       <div className="flex flex-1 flex-col gap-1">
         {navItems.map((item) => (
           <NavItem