chore: persist vercel project configuration

.gitignore

@@ -48,3 +48,4 @@ backend/**/__pycache__/
 backend/ai_router/__pycache__/
 .env.keys
 backend/.env.keys
+.vercel

vercel.json

@@ -0,0 +1,13 @@
+{
+  "experimentalServices": {
+    "frontend": {
+      "entrypoint": "frontend",
+      "routePrefix": "/",
+      "framework": "nextjs"
+    },
+    "backend": {
+      "entrypoint": "backend",
+      "routePrefix": "/_/backend"
+    }
+  }
+}