🧪 Add test for NewManager in internal/service

[adcondev]

• 🎯 What: The NewManager function in internal/service/service.go was lacking unit tests.
• 📊 Coverage: Added coverage for the successful instantiation of a Manager struct when a Variant is passed, effectively ensuring that the returned Manager holds the identically passed Variant.
• ✨ Result: Increases the overall test coverage within internal/service and safeguards against regressions during future refactorings.

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PR created automatically by Jules for task 6111791034922660791 started by @adcondev

[google-labs-jules]

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[github-actions]

⚡ Benchmark Results

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