Set Booking.com send_ready() to True

room_cal/service_api/_booking.py

@@ -592,7 +592,7 @@ class _BookingClient:
     ]
 
   def send_ready(self) -> bool:
-    return False
+    return True
 
   async def get_thread(self, reservation_id: str) -> BookingThread:
     """Fetch a conversation thread and its messages by reservation ID."""