feat(NcSelect): use @nextcloud/vue-select 4.0.0

[pringelmann]

☑️ Resolves

Removes the stale TODO in NcSelect by switching from vue-select beta to NC fork.

🚧 Notes

• CSS is inlined in the bundle, so the separate .../dist/vue-select.css import is gone.
• @nextcloud/vue-select is inlined in vitest.config.ts so its bundled CSS import goes through Vite's transform.
• The fork wires up the limit prop, which was a no-op in upstream beta.

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.58%. Comparing base (a85904a) to head (fc07e88).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8423      +/-   ##
==========================================
+ Coverage   54.08%   54.58%   +0.50%     
==========================================
  Files         104      104              
  Lines        3400     3400              
  Branches      992      993       +1     
==========================================
+ Hits         1839     1856      +17     
+ Misses       1322     1305      -17     
  Partials      239      239              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[susnux]

@pringelmann tests are related