fix: improve API extension dialog controls

[lyzno1]

Summary

• make the API-based extension modal fully controlled via open/onOpenChange
• add DialogTitle/DialogCloseButton and disable outside-click dismissal
• force-render the delete alert dialog backdrop and clean up touched legacy styling/icons

Tests

• pnpm -C web test app/components/header/account-setting/api-based-extension-page/tests
• pnpm --dir web type-check

[codecov]

Codecov Report

❌ Patch coverage is 92.59259% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.94%. Comparing base (730a0be) to head (1de3116).

Files with missing lines	Patch %	Lines
...account-setting/api-based-extension-page/index.tsx	85.71%	2 Missing ⚠️
...ount-setting/api-based-extension-page/selector.tsx	90.47%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #36323      +/-   ##
==========================================
- Coverage   85.94%   85.94%   -0.01%     
==========================================
  Files        4454     4455       +1     
  Lines      211360   211095     -265     
  Branches    39501    39440      -61     
==========================================
- Hits       181653   181420     -233     
+ Misses      26499    26480      -19     
+ Partials     3208     3195      -13     

Flag	Coverage Δ
dify-ui	94.59% <ø> (ø)
web	86.55% <92.59%> (-0.01%)	⬇️

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