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/fast-glob/out/utils/stream.d.ts

@@ -0,0 +1,4 @@
+/// <reference types="node" />
+/// <reference types="node" />
+import { Readable } from 'stream';
+export declare function merge(streams: Readable[]): NodeJS.ReadableStream;