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

node-network-app/node_modules/util-deprecate/node.js

@@ -0,0 +1,6 @@
+
+/**
+ * For Node.js, simply re-export the core `util.deprecate` function.
+ */
+
+module.exports = require('util').deprecate;