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/.vite/deps/react-dom_client.js

@@ -0,0 +1,38 @@
+import {
+  require_react_dom
+} from "./chunk-XBADDG25.js";
+import {
+  __commonJS
+} from "./chunk-UYNX3HOC.js";
+
+// node_modules/react-dom/client.js
+var require_client = __commonJS({
+  "node_modules/react-dom/client.js"(exports) {
+    var m = require_react_dom();
+    if (false) {
+      exports.createRoot = m.createRoot;
+      exports.hydrateRoot = m.hydrateRoot;
+    } else {
+      i = m.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED;
+      exports.createRoot = function(c, o) {
+        i.usingClientEntryPoint = true;
+        try {
+          return m.createRoot(c, o);
+        } finally {
+          i.usingClientEntryPoint = false;
+        }
+      };
+      exports.hydrateRoot = function(c, h, o) {
+        i.usingClientEntryPoint = true;
+        try {
+          return m.hydrateRoot(c, h, o);
+        } finally {
+          i.usingClientEntryPoint = false;
+        }
+      };
+    }
+    var i;
+  }
+});
+export default require_client();
+//# sourceMappingURL=react-dom_client.js.map