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/resolve/test/resolver/invalid_main/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "invalid_main",
+  "main": [
+    "why is this a thing",
+    "srsly omg wtf"
+  ]
+}