Use quoted type strings in cast() expressions

[Copilot]

Addresses review feedback from PR #40 to use quoted type strings in cast() expressions for consistency with modern Python typing practices.

Changes

• Updated app/auth/jwt.py: Changed cast(str, ...) to cast("str", ...) in both JWT token creation functions

# Before
return cast(str, jwt.encode(...))

# After  
return cast("str", jwt.encode(...))

Affects create_access_token() and create_refresh_token() functions.

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[Neiland85]

Closing this PR. The changes no longer align with the updated architecture and dependency model introduced in the December 2025 refactor.

This contribution is now obsolete and would add noise rather than value to the current codebase.