🧪 Add unit tests for ValidatePassword in Auth Manager

[adcondev]

🎯 What: The ValidatePassword method in internal/auth/Manager was missing unit tests, leaving its password validation and configuration fallback logic unverified.
📊 Coverage: Achieved 100% statement coverage for the ValidatePassword method. New tests cover enabled/disabled states, invalid configurations (bad base64, invalid bcrypt), and valid/invalid password matches.
✨ Result: Increased reliability of the auth component by ensuring edge cases correctly match the expected boolean output without regressions.

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PR created automatically by Jules for task 17122858187111243015 started by @adcondev

[google-labs-jules]

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[github-actions]

⚡ Benchmark Results

⚠️ No benchmarks found in the current codebase.

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[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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