fix(next-auth): add missing middleware wrapper type to auth function

[k-taro56]

☕️ Reasoning

This PR adds a missing TypeScript type overload for the auth function when used as a middleware wrapper pattern

🧢 Checklist

• Documentation
• Tests
• Ready to be merged

🎫 Affected issues

📌 Resources

• Security guidelines
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• Code of conduct
• Contributing to Open Source

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
auth-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 3, 2025 3:33pm

1 Skipped Deployment

Name	Status	Preview	Comments	Updated (UTC)
next-auth-docs	⬜️ Ignored (Inspect)			Jun 3, 2025 3:33pm

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39.20%. Comparing base (22c1b8b) to head (e0aabad).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13026   +/-   ##
=======================================
  Coverage   39.19%   39.20%           
=======================================
  Files         200      200           
  Lines       31615    31620    +5     
  Branches     1381     1381           
=======================================
+ Hits        12391    12396    +5     
  Misses      19224    19224           

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