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/update-browserslist-db/check-npm-version.js

@@ -0,0 +1,17 @@
+let { execSync } = require('child_process')
+let pico = require('picocolors')
+
+try {
+  let version = parseInt(execSync('npm -v'))
+  if (version <= 6) {
+    process.stderr.write(
+      pico.red(
+        'Update npm or call ' +
+          pico.yellow('npx browserslist@latest --update-db') +
+          '\n'
+      )
+    )
+    process.exit(1)
+  }
+  // eslint-disable-next-line no-unused-vars
+} catch (e) {}