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-network-app/node_modules/postcss-js/sync.js

@@ -0,0 +1,12 @@
+let postcss = require('postcss')
+
+let parse = require('./parser')
+let processResult = require('./process-result')
+
+module.exports = function (plugins) {
+  let processor = postcss(plugins)
+  return input => {
+    let result = processor.process(input, { parser: parse, from: undefined })
+    return processResult(result)
+  }
+}