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/deep-is/example/cmp.js

@@ -0,0 +1,11 @@
+var equal = require('../');
+console.dir([
+    equal(
+        { a : [ 2, 3 ], b : [ 4 ] },
+        { a : [ 2, 3 ], b : [ 4 ] }
+    ),
+    equal(
+        { x : 5, y : [6] },
+        { x : 5, y : 6 }
+    )
+]);