chore: deployment debugging - minimal middleware, health api, and nextjs upgrade

src/app/api/health/route.ts

@@ -0,0 +1,12 @@
+import { NextResponse } from 'next/server';
+
+export async function GET() {
+    return NextResponse.json({
+        status: 'ok',
+        time: new Date().toISOString(),
+        env: {
+            supabaseUrl: process.env.NEXT_PUBLIC_SUPABASE_URL ? 'set' : 'missing',
+            supabaseAnonKey: process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY ? 'set' : 'missing'
+        }
+    });
+}