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/eslint/messages/eslintrc-plugins.js

@@ -0,0 +1,24 @@
+"use strict";
+
+module.exports = function({ plugins }) {
+
+    const isArrayOfStrings = typeof plugins[0] === "string";
+
+    return `
+A config object has a "plugins" key defined as an array${isArrayOfStrings ? " of strings" : ""}.
+
+Flat config requires "plugins" to be an object in this form:
+
+    {
+        plugins: {
+            ${isArrayOfStrings && plugins[0] ? plugins[0] : "namespace"}: pluginObject
+        }
+    }
+
+Please see the following page for information on how to convert your config object into the correct format:
+https://eslint.org/docs/latest/use/configure/migration-guide#importing-plugins-and-custom-parsers
+
+If you're using a shareable config that you cannot rewrite in flat config format, then use the compatibility utility:
+https://eslint.org/docs/latest/use/configure/migration-guide#using-eslintrc-configs-in-flat-config
+`;
+};