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/semver/internal/lrucache.js

@@ -0,0 +1,42 @@
+'use strict'
+
+class LRUCache {
+  constructor () {
+    this.max = 1000
+    this.map = new Map()
+  }
+
+  get (key) {
+    const value = this.map.get(key)
+    if (value === undefined) {
+      return undefined
+    } else {
+      // Remove the key from the map and add it to the end
+      this.map.delete(key)
+      this.map.set(key, value)
+      return value
+    }
+  }
+
+  delete (key) {
+    return this.map.delete(key)
+  }
+
+  set (key, value) {
+    const deleted = this.delete(key)
+
+    if (!deleted && value !== undefined) {
+      // If cache is full, delete the least recently used item
+      if (this.map.size >= this.max) {
+        const firstKey = this.map.keys().next().value
+        this.delete(firstKey)
+      }
+
+      this.map.set(key, value)
+    }
+
+    return this
+  }
+}
+
+module.exports = LRUCache