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.d.ts

@@ -0,0 +1,3 @@
+import type { Config } from './types/config'
+declare const config: Config
+export = config