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/test/str.js

@@ -0,0 +1,46 @@
+'use strict';
+
+var test = require('tape');
+var stringify = require('../');
+
+test('simple object', function (t) {
+    t.plan(1);
+    var obj = { c: 6, b: [4,5], a: 3, z: null };
+    t.equal(stringify(obj), '{"a":3,"b":[4,5],"c":6,"z":null}');
+});
+
+test('object with undefined', function (t) {
+    t.plan(1);
+    var obj = { a: 3, z: undefined };
+    t.equal(stringify(obj), '{"a":3}');
+});
+
+test('object with null', function (t) {
+    t.plan(1);
+    var obj = { a: 3, z: null };
+    t.equal(stringify(obj), '{"a":3,"z":null}');
+});
+
+test('object with NaN and Infinity', function (t) {
+    t.plan(1);
+    var obj = { a: 3, b: NaN, c: Infinity };
+    t.equal(stringify(obj), '{"a":3,"b":null,"c":null}');
+});
+
+test('array with undefined', function (t) {
+    t.plan(1);
+    var obj = [4, undefined, 6];
+    t.equal(stringify(obj), '[4,null,6]');
+});
+
+test('object with empty string', function (t) {
+    t.plan(1);
+    var obj = { a: 3, z: '' };
+    t.equal(stringify(obj), '{"a":3,"z":""}');
+});
+
+test('array with empty string', function (t) {
+    t.plan(1);
+    var obj = [4, '', 6];
+    t.equal(stringify(obj), '[4,"",6]');
+});