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/function-bind/.eslintrc

@@ -0,0 +1,21 @@
+{
+	"root": true,
+
+	"extends": "@ljharb",
+
+	"rules": {
+		"func-name-matching": 0,
+		"indent": [2, 4],
+		"no-new-func": [1],
+	},
+
+	"overrides": [
+		{
+			"files": "test/**",
+			"rules": {
+				"max-lines-per-function": 0,
+				"strict": [0]
+			},
+		},
+	],
+}