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/tailwindcss/defaultConfig.js

@@ -0,0 +1,2 @@
+let defaultConfig = require('./lib/public/default-config')
+module.exports = (defaultConfig.__esModule ? defaultConfig : { default: defaultConfig }).default