feat: Add presence heartbeat for Matrix online status

- matrix-gateway: POST /internal/matrix/presence/online endpoint
- usePresenceHeartbeat hook with activity tracking
- Auto away after 5 min inactivity
- Offline on page close/visibility change
- Integrated in MatrixChatRoom component

telegram-infrastructure/telegram-gateway/app/models.py

@@ -9,6 +9,7 @@ class TelegramUpdateEvent(BaseModel):
     chat_id: int
     user_id: int
     text: Optional[str] = None
+    metadata: Optional[Dict[str, Any]] = None
     raw_update: Dict[str, Any]