refactor: remove duplicate auth module and centralize authentication logic

[spike014]

• Remove duplicate src/lib/auth.ts file
• Update middleware.ts to use @/modules/auth/utils/auth-utils
• Maintain backward compatibility with aliasing
• Reduce code duplication and improve project structure

🤖 Generated with Claude Code

FYI: Claude Code fixed it with my prompts. @ifindev

Summary by CodeRabbit

• Refactor

  • Centralized authentication utilities and updated middleware to use the shared module.
  • No changes to sign-in, session handling, or redirect behavior.

• Chores

  • Removed deprecated authentication code to reduce duplication and streamline maintenance.

[coderabbitai]

Walkthrough

Authentication utility source is switched in middleware.ts to an aliased path. The legacy auth implementation at src/lib/auth.ts is deleted. Middleware logic and exported signatures remain unchanged.

Changes

Cohort / File(s)	Summary of Changes
Auth import refactor middleware.ts	Updated import from ./src/lib/auth to @/modules/auth/utils/auth-utils with aliasing (getAuthInstance as getAuth); no logic changes in middleware.
Legacy auth module removal src/lib/auth.ts	Deleted the entire file, removing the prior getAuth singleton factory and its Better-Auth/DB integration.

Sequence Diagram(s)

(no diagrams)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

A whisk of code, a hop to new burrows bright,
Old auth burrow gone, new tunnel in sight.
I twitch my nose at imports neat,
Same path through woods, just lighter feet.
Carrot commits stacked—merge tonight! 🥕

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title “refactor: remove duplicate auth module and centralize authentication logic” directly summarizes the primary change in this pull request by highlighting the removal of the redundant auth module and the shift to a centralized authentication utility, which aligns precisely with the modifications in src/lib/auth.ts deletion and the updated import in middleware.ts. It is concise, specific, and free of extraneous detail, making the intent immediately clear to reviewers.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate Docstrings

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment

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[ifindev]

Great catch @spike014! I noticed the issue last week, but got busy with other work. So, thanks for the fix!