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`

hooks/use-system-health.ts

@@ -5,7 +5,7 @@ import { fetcher } from "@/lib/swr/fetcher";
 export function useSystemHealth() {
   const { data, error, isLoading, isValidating, mutate } =
     useSWR<SystemHealthData>("/api/admin/system-health", fetcher, {
-      revalidateOnFocus: true,
+      revalidateOnFocus: false,
       dedupingInterval: 10_000,
     });