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/@babel/helper-validator-identifier/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "@babel/helper-validator-identifier",
+  "version": "7.28.5",
+  "description": "Validate identifier/keywords name",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/babel/babel.git",
+    "directory": "packages/babel-helper-validator-identifier"
+  },
+  "license": "MIT",
+  "publishConfig": {
+    "access": "public"
+  },
+  "main": "./lib/index.js",
+  "exports": {
+    ".": {
+      "types": "./lib/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./package.json": "./package.json"
+  },
+  "devDependencies": {
+    "@unicode/unicode-17.0.0": "^1.6.10",
+    "charcodes": "^0.2.0"
+  },
+  "engines": {
+    "node": ">=6.9.0"
+  },
+  "author": "The Babel Team (https://babel.dev/team)",
+  "type": "commonjs"
+}