fix(conversations): stop a cancelled catch-up from running on

The per-room message catch-up wraps each room in runCatching, which also
catches the CancellationException raised when the sync is stopped. The
failure was logged and the loop moved on to the next room, so a sync that
had been cancelled kept issuing requests for every remaining room.

Rethrow the cancellation so the loop ends with the scope that owns it.

Assisted-by: Claude Code:claude-opus-5
Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

Author: AndyScherzinger

app/src/main/java/com/nextcloud/talk/conversationlist/data/network/OfflineFirstConversationsRepository.kt

@@ -336,7 +336,10 @@ class OfflineFirstConversationsRepository @Inject constructor(
                                 unreadMessages = room.unreadMessages
                             )
                         }
-                            .onFailure { Log.e(TAG, "Message catch-up failed for room ${room.token}", it) }
+                            .onFailure {
+                                if (it is CancellationException) throw it
+                                Log.e(TAG, "Message catch-up failed for room ${room.token}", it)
+                            }
                     }
                 }
             }