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_modules/.vite/deps_temp_9c9ec632/react.js

@@ -0,0 +1,5 @@
+import {
+  require_react
+} from "./chunk-REFQX4J5.js";
+export default require_react();
+//# sourceMappingURL=react.js.map