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/index.browser.js

@@ -0,0 +1,34 @@
+import { urlAlphabet } from './url-alphabet/index.js'
+let random = bytes => crypto.getRandomValues(new Uint8Array(bytes))
+let customRandom = (alphabet, defaultSize, getRandom) => {
+  let mask = (2 << (Math.log(alphabet.length - 1) / Math.LN2)) - 1
+  let step = -~((1.6 * mask * defaultSize) / alphabet.length)
+  return (size = defaultSize) => {
+    let id = ''
+    while (true) {
+      let bytes = getRandom(step)
+      let j = step | 0
+      while (j--) {
+        id += alphabet[bytes[j] & mask] || ''
+        if (id.length === size) return id
+      }
+    }
+  }
+}
+let customAlphabet = (alphabet, size = 21) =>
+  customRandom(alphabet, size, random)
+let nanoid = (size = 21) =>
+  crypto.getRandomValues(new Uint8Array(size)).reduce((id, byte) => {
+    byte &= 63
+    if (byte < 36) {
+      id += byte.toString(36)
+    } else if (byte < 62) {
+      id += (byte - 26).toString(36).toUpperCase()
+    } else if (byte > 62) {
+      id += '-'
+    } else {
+      id += '_'
+    }
+    return id
+  }, '')
+export { nanoid, customAlphabet, customRandom, urlAlphabet, random }