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

src/features/messenger/api/getChannelMessages.ts

@@ -0,0 +1,30 @@
+import type { Message } from '../types/messenger';
+
+export async function getChannelMessages(
+  channelId: string,
+  limit: number = 50,
+  before?: string
+): Promise<Message[]> {
+  let url = `/api/messaging/channels/${channelId}/messages?limit=${limit}`;
+  if (before) {
+    url += `&before=${encodeURIComponent(before)}`;
+  }
+
+  const res = await fetch(url, {
+    method: 'GET',
+    headers: {
+      'Accept': 'application/json',
+      'X-User-Id': 'user:admin', // TODO: get from auth context
+    },
+  });
+
+  if (!res.ok) {
+    throw new Error(`Failed to fetch messages: ${res.status}`);
+  }
+
+  return res.json();
+}
+
+
+
+