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/lodash.merge/README.md

@@ -0,0 +1,18 @@
+# lodash.merge v4.6.2
+
+The [Lodash](https://lodash.com/) method `_.merge` exported as a [Node.js](https://nodejs.org/) module.
+
+## Installation
+
+Using npm:
+```bash
+$ {sudo -H} npm i -g npm
+$ npm i --save lodash.merge
+```
+
+In Node.js:
+```js
+var merge = require('lodash.merge');
+```
+
+See the [documentation](https://lodash.com/docs#merge) or [package source](https://github.com/lodash/lodash/blob/4.6.2-npm-packages/lodash.merge) for more details.