Fix: close consensus node gRPC channels in Client.close() (hiero-ledger#2203)

Signed-off-by: Mohit Yadav <ymohit799057@gmail.com>

Author: mohityadav8

src/hiero_sdk_python/client/client.py

@@ -200,12 +200,18 @@ def close(self) -> None:
         Closes any open gRPC channels and frees resources.
         Call this when you are done using the Client to ensure a clean shutdown.
         """
+        # Close mirror channel
         if self.mirror_channel is not None:
             self.mirror_channel.close()
             self.mirror_channel = None
 
         self.mirror_stub = None
 
+        # Fix: Close all consensus node channels
+        if self.network and self.network.nodes:
+            for node in self.network.nodes:
+                node._close()
+
     def set_transport_security(self, enabled: bool) -> Client:
         """
         Enable or disable TLS for consensus node connections.