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/fs.realpath/package.json

@@ -0,0 +1,26 @@
+{
+  "name": "fs.realpath",
+  "version": "1.0.0",
+  "description": "Use node's fs.realpath, but fall back to the JS implementation if the native one fails",
+  "main": "index.js",
+  "dependencies": {},
+  "devDependencies": {},
+  "scripts": {
+    "test": "tap test/*.js --cov"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/isaacs/fs.realpath.git"
+  },
+  "keywords": [
+    "realpath",
+    "fs",
+    "polyfill"
+  ],
+  "author": "Isaac Z. Schlueter <i@izs.me> (http://blog.izs.me/)",
+  "license": "ISC",
+  "files": [
+    "old.js",
+    "index.js"
+  ]
+}