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/eastasianwidth/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "eastasianwidth",
+  "version": "0.2.0",
+  "description": "Get East Asian Width from a character.",
+  "main": "eastasianwidth.js",
+  "files": [
+    "eastasianwidth.js"
+  ],
+  "scripts": {
+    "test": "mocha"
+  },
+  "repository": "git://github.com/komagata/eastasianwidth.git",
+  "author": "Masaki Komagata",
+  "license": "MIT",
+  "devDependencies": {
+    "mocha": "~1.9.0"
+  }
+}