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/eslint/messages/whitespace-found.js

@@ -0,0 +1,11 @@
+"use strict";
+
+module.exports = function(it) {
+    const { pluginName } = it;
+
+    return `
+ESLint couldn't find the plugin "${pluginName}". because there is whitespace in the name. Please check your configuration and remove all whitespace from the plugin name.
+
+If you still can't figure out the problem, please stop by https://eslint.org/chat/help to chat with the team.
+`.trimStart();
+};