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/fast-json-stable-stringify/example/key_cmp.js

@@ -0,0 +1,7 @@
+var stringify = require('../');
+
+var obj = { c: 8, b: [{z:6,y:5,x:4},7], a: 3 };
+var s = stringify(obj, function (a, b) {
+    return a.key < b.key ? 1 : -1;
+});
+console.log(s);

node_modules/fast-json-stable-stringify/example/nested.js

@@ -0,0 +1,3 @@
+var stringify = require('../');
+var obj = { c: 8, b: [{z:6,y:5,x:4},7], a: 3 };
+console.log(stringify(obj));

node_modules/fast-json-stable-stringify/example/str.js

@@ -0,0 +1,3 @@
+var stringify = require('../');
+var obj = { c: 6, b: [4,5], a: 3 };
+console.log(stringify(obj));

node_modules/fast-json-stable-stringify/example/value_cmp.js

@@ -0,0 +1,7 @@
+var stringify = require('../');
+
+var obj = { d: 6, c: 5, b: [{z:3,y:2,x:1},9], a: 10 };
+var s = stringify(obj, function (a, b) {
+    return a.value < b.value ? 1 : -1;
+});
+console.log(s);