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/index.js

@@ -0,0 +1,4 @@
+'use strict';
+const ansiRegex = require('ansi-regex');
+
+module.exports = string => typeof string === 'string' ? string.replace(ansiRegex(), '') : string;