refactor: migrate middleware.ts to proxy.ts (Next.js 16)

proxy.ts

@@ -0,0 +1,16 @@
+import { neonAuthMiddleware } from "@neondatabase/auth/next/server";
+
+// Next.js 16 renamed middleware to proxy
+// neonAuthMiddleware returns a middleware function, we export it as proxy
+export const proxy = neonAuthMiddleware({
+  // Redirects unauthenticated users to sign-in page
+  loginUrl: "/auth/sign-in",
+});
+
+export const config = {
+  matcher: [
+    // Protected routes requiring authentication
+    "/dashboard/:path*",
+    "/account/:path*",
+  ],
+};