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/postcss-js/index.js

@@ -0,0 +1,11 @@
+let async = require('./async')
+let objectify = require('./objectifier')
+let parse = require('./parser')
+let sync = require('./sync')
+
+module.exports = {
+  objectify,
+  parse,
+  async,
+  sync
+}