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/process-result.js

@@ -0,0 +1,11 @@
+let objectify = require('./objectifier')
+
+module.exports = function processResult(result) {
+  if (console && console.warn) {
+    result.warnings().forEach(warn => {
+      let source = warn.plugin || 'PostCSS'
+      console.warn(source + ': ' + warn.text)
+    })
+  }
+  return objectify(result.root)
+}