feat: Validate Config Existence in config rm

[bpujol]

Enhanced the config rm command to check if the specified configuration exists before attempting to remove it.
Modified the deleteCmd function in config/cli.go to include a call to validateServerExistence, ensuring the configuration is present.
If the configuration does not exist, the command now returns an error, preventing further execution and improving user feedback.

This change addresses user concerns about the lack of feedback when removing non-existent configurations, providing a clearer and more robust user experience.

• [ x] All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• [x ] The pull request is targeting the dev branch.
• [x ] The code has been validated to compile successfully by running go vet ./....
• [x ] The code has been formatted properly using go fmt ./....

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