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/strip-ansi-cjs/index.d.ts

@@ -0,0 +1,17 @@
+/**
+Strip [ANSI escape codes](https://en.wikipedia.org/wiki/ANSI_escape_code) from a string.
+
+@example
+```
+import stripAnsi = require('strip-ansi');
+
+stripAnsi('\u001B[4mUnicorn\u001B[0m');
+//=> 'Unicorn'
+
+stripAnsi('\u001B]8;;https://github.com\u0007Click\u001B]8;;\u0007');
+//=> 'Click'
+```
+*/
+declare function stripAnsi(string: string): string;
+
+export = stripAnsi;