🧪 Add tests for GetFamilyNames and refactor implementation

[adcondev]

🎯 What: The GetFamilyNames function in internal/service/registry.go was hardcoded and lacking tests.
📊 Coverage: Added a test (TestGetFamilyNames) verifying that GetFamilyNames returns the keys from GetServiceRegistry() in sorted order, covering its intended behaviour completely.
✨ Result: The GetFamilyNames function is now dynamic and is fully tested.

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PR created automatically by Jules for task 3930117566554857831 started by @adcondev

[google-labs-jules]

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[github-actions]

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