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/titles/resolve/route.ts

@@ -1,8 +1,7 @@
-import { headers } from "next/headers";
 import type { NextRequest } from "next/server";
 import { NextResponse } from "next/server";
 import { z } from "zod";
-import { auth } from "@/lib/auth/server";
+import { getSession } from "@/lib/auth/session";
 import { importTitle } from "@/lib/services/metadata";
 
 const bodySchema = z.object({
@@ -11,9 +10,7 @@ const bodySchema = z.object({
 });
 
 export async function POST(req: NextRequest) {
-  const session = await auth.api.getSession({
-    headers: await headers(),
-  });
+  const session = await getSession();
   if (!session) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
   }