Fix cluster master uptime to show actual server start time instead of instance creation time

vidai/cluster_master.py

@@ -136,6 +136,7 @@ class ClusterMaster:
     async def start(self) -> None:
         """Start the cluster master server."""
         self.running = True
+        self.start_time = time.time()  # Update start time when server actually starts
         print(f"Cluster master started on port {self.port} (secure websocket)")
 
         # Generate/load SSL certificate