fix(dev): proxy the messages WebSocket through Vite, which stops a reset killing the dev server

The Vite dev proxy had no `ws: true` on /api, so the in-app messages socket
(/api/messages/ws) was an upgrade nobody handled: it never connected on :5173,
and the first reset on it (a closed tab, a dropped connection) threw an
unhandled ECONNRESET that took the whole dev server down. Reproduced with a raw
upgrade + RST (dev server dead); with `ws: true` the backend answers the
upgrade, the dev server survives the reset and a closed tab, and the signed-in
socket is accepted through the proxy.

frontend/vite.config.ts

@@ -11,7 +11,10 @@ const target = "http://127.0.0.1:8080";
 // server returns to :5173 instead of the fixed :8080 callback. (Both are registered in the console.)
 const proxyOpts = { target, changeOrigin: false };
 const proxy = {
-  "/api": proxyOpts,
+  // ws: the in-app messages socket (/api/messages/ws) is a WebSocket. Without it Vite hands that upgrade
+  // to nobody, so the socket never connects on :5173 — and the first reset on it (a closed tab, a dropped
+  // connection) throws an unhandled ECONNRESET that takes the whole dev server down.
+  "/api": { ...proxyOpts, ws: true },
   "/auth": proxyOpts,
   "/healthz": proxyOpts,
 };