feat: smooth view transitions, no skeleton flash

User pain point: skeleton loading.tsx files made the app feel like
a sequence of page reloads, exposing backend latency. Replaced with
a single 1px shimmer bar + crossfade via React's <ViewTransition>.

Changes:
- Enable experimental.viewTransition in next.config.ts
- Add SmoothViewTransition wrapper (ViewTransition name=page-content)
- Add LoadingFade component: thin animated bar instead of skeleton
- Add RouteAnnouncer for a11y (screen readers + focus reset)
- Add ::view-transition-old/new CSS for the crossfade (220ms, no
  jarring slide, respects prefers-reduced-motion)
- Wrap admin/tuxedo/IRD layout children in SmoothViewTransition
  (sidebar/header/footer stay mounted; only the body fades)
- Replace 19 skeleton loading.tsx files with the fade component

Result: navigation now feels like a single app, not a series of
preload-and-render events. The user never sees a 'skeleton of the
page they're about to load.'

src/app/tuxedo/layout.tsx

@@ -1,4 +1,5 @@
 import type { Metadata, Viewport } from "next";
+import { SmoothViewTransition } from "@/components/transitions/SmoothViewTransition";
 
 const BASE_URL = process.env.NEXT_PUBLIC_SITE_URL ?? "https://routecommerce.com";
 
@@ -107,7 +108,12 @@ export default function TuxedoLayout({ children }: { children: React.ReactNode }
       <div className="fixed inset-0 pointer-events-none">
         <div className="absolute top-0 right-0 w-[500px] h-[500px] bg-emerald-500/10 rounded-full blur-[120px]" />
       </div>
-      <div className="relative">{children}</div>
+      {/* The storefront backdrop and ambient orbs are persistent. The
+          page body itself crossfades between routes via the View
+          Transitions API. */}
+      <div id="page-content" className="relative outline-none">
+        <SmoothViewTransition>{children}</SmoothViewTransition>
+      </div>
     </div>
   );
 }