fix(#990): use a dedicated host calculation for authjs

[phoenix-ru]

🔗 Linked issue

Closes #990

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

After #984, one of well-hidden bugs was uncovered. authjs does a lot of implicit and unintuitive URL manipulation under the hood, leading to only /api/auth path working correctly out-of-the-box.
This PR reworks nuxtAuthHandler passing parameters to authjs to account for the inconsistency. Instead of passing full request URL or just its origin, we now pass baseURL to authjs handler.
This leads to no implicit /api/auth being added and also callback paths being built correctly.

📝 Checklist

• I have linked an issue or discussion.
• I have added tests (if possible).
• I have updated the documentation accordingly.

[pkg-pr-new]

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npm i https://pkg.pr.new/@sidebase/nuxt-auth@992 

commit: e76a9b8