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/@nodelib/fs.stat/out/providers/async.d.ts

@@ -0,0 +1,4 @@
+import type Settings from '../settings';
+import type { ErrnoException, Stats } from '../types';
+export declare type AsyncCallback = (error: ErrnoException, stats: Stats) => void;
+export declare function read(path: string, settings: Settings, callback: AsyncCallback): void;