Add TURN servers back for restrictive NAT support

- Re-add metered.ca TURN servers on ports 80 and 443
- Keep Google STUN servers for NAT detection
- Enables connections through restrictive firewalls

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/App.jsx

@@ -7,7 +7,20 @@ const API_URL = 'https://api.ronde.vu';
 const RTC_CONFIG = {
   iceServers: [
     { urls: 'stun:stun.l.google.com:19302' },
-    { urls: 'stun:stun1.l.google.com:19302' }
+    { urls: 'stun:stun1.l.google.com:19302' },
+    {
+      urls: "stun:stun.relay.metered.ca:80",
+    },
+    {
+      urls: "turn:standard.relay.metered.ca:80",
+      username: "e03a51621b4f11ffbed3addd",
+      credential: "QPjJzPau1Ng5S0dq",
+    },
+    {
+      urls: "turn:standard.relay.metered.ca:443",
+      username: "e03a51621b4f11ffbed3addd",
+      credential: "QPjJzPau1Ng5S0dq",
+    },
   ]
 };