Fix mypy type annotation errors

[RinZ27]

I've addressed the mypy type annotation failures by adding explicit return types and correcting type mismatches across the auth and API modules.

This fix covers:

• Adding missing return type annotations.
• Correcting 'Any' return types to match expected types.
• Fixing type mismatches (e.g., casting rowcount to int/bool).

This should resolve the mypy job failures and ensure consistent type safety. Verified locally.

[RinZ27]

Closing duplicate PR; changes integrated into #11.