Fix gateway exit code to enable systemd auto-restart on connection failure

- Updated the start_gateway function to return a boolean indicating success or failure, allowing for better control over exit codes.
- Modified the main function to handle gateway startup failures, ensuring systemd can automatically restart on transient errors.
- Enhanced error handling in the hermes_cli gateway to exit with code 1 if the gateway fails to connect to any platform.

hermes_cli/gateway.py

@@ -360,7 +360,11 @@ def run_gateway(verbose: bool = False):
     print("└─────────────────────────────────────────────────────────┘")
     print()
     
-    asyncio.run(start_gateway())
+    # Exit with code 1 if gateway fails to connect any platform,
+    # so systemd Restart=on-failure will retry on transient errors
+    success = asyncio.run(start_gateway())
+    if not success:
+        sys.exit(1)
 
 
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