Refactor auth session handling and server actions across app

- Overhaul `lib/auth/server.ts` and `lib/auth/session.ts`; update all API
  routes and server actions to use the revised session pattern
- Refactor server actions (settings, titles, watchlist, setup) for
  consistency with new auth layer
- Extract `SetupForm` into its own client component with `useActionState`,
  animated steps, and copyable env snippets
- Move landing page redirect logic into `app/page.tsx`; slim down
  `LandingPage` component
- Add `proxy.ts` for local dev proxying
- Minor cleanup to `NavBar`, `MobileTabBar`, and `TitleCard`

app/api/search/route.ts

@@ -1,6 +1,5 @@
-import { headers } from "next/headers";
 import { type NextRequest, NextResponse } from "next/server";
-import { auth } from "@/lib/auth/server";
+import { getSession } from "@/lib/auth/session";
 import { isTmdbConfigured } from "@/lib/config";
 import {
   searchMovies,
@@ -12,9 +11,7 @@ import { tmdbImageUrl } from "@/lib/tmdb/image";
 import type { TmdbSearchResponse } from "@/lib/tmdb/types";
 
 export async function GET(req: NextRequest) {
-  const session = await auth.api.getSession({
-    headers: await headers(),
-  });
+  const session = await getSession();
   if (!session) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
   }