Fix relay server issues: images and URL display

1. Images not showing through relay:
   - Use getApiUrl() for image paths in relay mode
   - Add password as query param for img tags (can't use headers)

2. URL not updating in desktop app:
   - Set _connected=True before on_session_id callback fires
   - Ensures update_ip_label() shows relay URL immediately

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

relay_client.py

@@ -141,6 +141,8 @@ class RelayClient:
 
         if response.get("type") == "auth_response":
             if response.get("success"):
+                # Mark as connected before callbacks so update_ip_label works
+                self._connected = True
                 new_session_id = response.get("sessionId")
                 if new_session_id and new_session_id != self.session_id:
                     self.session_id = new_session_id