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

services/node-registry/app/__init__.py

@@ -0,0 +1,13 @@
+"""
+Node Registry Service Application
+Full implementation with database integration
+"""
+
+from .main import app
+from .models import Base, Node, NodeProfile, HeartbeatLog
+from .database import get_db, engine
+from . import crud, schemas
+
+__version__ = "1.0.0"
+__all__ = ["app", "Base", "Node", "NodeProfile", "HeartbeatLog", "get_db", "engine", "crud", "schemas"]
+