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/semver/internal/debug.js

@@ -0,0 +1,11 @@
+'use strict'
+
+const debug = (
+  typeof process === 'object' &&
+  process.env &&
+  process.env.NODE_DEBUG &&
+  /\bsemver\b/i.test(process.env.NODE_DEBUG)
+) ? (...args) => console.error('SEMVER', ...args)
+  : () => {}
+
+module.exports = debug