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/.vite/deps/react-dom.js

@@ -0,0 +1,6 @@
+import {
+  require_react_dom
+} from "./chunk-BCXODTBQ.js";
+import "./chunk-2YIMICFJ.js";
+export default require_react_dom();
+//# sourceMappingURL=react-dom.js.map