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/nanoid/non-secure/index.d.ts

@@ -0,0 +1,33 @@
+/**
+ * Generate URL-friendly unique ID. This method uses the non-secure
+ * predictable random generator with bigger collision probability.
+ *
+ * ```js
+ * import { nanoid } from 'nanoid/non-secure'
+ * model.id = nanoid() //=> "Uakgb_J5m9g-0JDMbcJqL"
+ * ```
+ *
+ * @param size Size of the ID. The default size is 21.
+ * @returns A random string.
+ */
+export function nanoid(size?: number): string
+
+/**
+ * Generate a unique ID based on a custom alphabet.
+ * This method uses the non-secure predictable random generator
+ * with bigger collision probability.
+ *
+ * @param alphabet Alphabet used to generate the ID.
+ * @param defaultSize Size of the ID. The default size is 21.
+ * @returns A random string generator.
+ *
+ * ```js
+ * import { customAlphabet } from 'nanoid/non-secure'
+ * const nanoid = customAlphabet('0123456789абвгдеё', 5)
+ * model.id = //=> "8ё56а"
+ * ```
+ */
+export function customAlphabet(
+  alphabet: string,
+  defaultSize?: number
+): (size?: number) => string