fix: add /v1 proxy entry to vite dev server config

Without this, /v1/chat/completions requests in local dev are served by
Vite instead of being proxied to the FastAPI backend.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

studio/frontend/vite.config.ts

@@ -17,6 +17,10 @@ export default defineConfig({
         target: "http://127.0.0.1:8000",
         changeOrigin: true,
       },
+      "/v1": {
+        target: "http://127.0.0.1:8000",
+        changeOrigin: true,
+      },
       "/seed/inspect": {
         target: "http://127.0.0.1:8004",
         changeOrigin: true,