fix(web): align Tailwind v4 CSS migration

[lyzno1]

Summary

This PR finishes the Tailwind v4 cleanup work around the existing CSS-first migration and removes the most visible compatibility leftovers in touched UI surfaces.

• removes the temporary Tailwind border compatibility layer from tailwind-core.css and replaces affected call sites with explicit design-system border tokens
• replaces unsafe outline-none usage with forced-color-safe outline-hidden, and adds visible focus-visible rings where needed
• migrates the recently touched legacy modal usages to @langgenius/dify-ui Dialog / AlertDialog primitives
• keeps dataset selection dialogs mounted and fully controlled through open / onOpenChange so Base UI enter/exit transitions can run
• consolidates the app export warning and secret-env export confirmation into one controlled AlertDialog root that switches content by mode
• removes the secret-env alert dialog close icon so the risk confirmation keeps explicit Cancel / Confirm semantics
• updates affected interactive rows/buttons to semantic controls with accessible focus states

Tailwind v4 status

The web app is now effectively using the v4 CSS-first architecture for the main Tailwind integration:

• no tailwind.config.* project config is used
• Tailwind entry CSS uses v4 directives such as @import, @theme, @theme inline, @utility, and CSS-level @plugin
• spacing-compatible arbitrary values in touched files were converted to v4 spacing utilities where exact, e.g. w-50, w-100, w-120

One intentional exception remains: @tailwindcss/typography is still registered through the CSS entry because develop MDX docs still depend on prose, prose-xl, prose-invert, and not-prose. Its current local JS customization can be migrated separately, but removing it in this PR would cause documentation styling regressions.

Testing

• pnpm exec eslint --fix --pass-on-unpruned-suppressions ... on touched files
• pnpm test -- app/components/app/configuration/dataset-config/select-dataset/__tests__/index.spec.tsx app/components/app/configuration/__tests__/configuration-view.spec.tsx app/components/workflow/nodes/knowledge-retrieval/__tests__/integration.spec.tsx app/components/workflow/__tests__/dsl-export-confirm-modal.spec.tsx app/components/app-sidebar/app-info/__tests__/app-info-modals.spec.tsx
• pnpm test -- app/components/app-sidebar/app-info/__tests__/app-operations.spec.tsx
• pnpm type-check

[codecov]

Codecov Report

❌ Patch coverage is 83.95062% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.81%. Comparing base (f8873ec) to head (e3cd0c0).

Files with missing lines	Patch %	Lines
...omponents/app-sidebar/app-info/app-info-modals.tsx	68.18%	7 Missing ⚠️
...figuration/dataset-config/select-dataset/index.tsx	84.37%	5 Missing ⚠️
...p/components/workflow/dsl-export-confirm-modal.tsx	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #35829      +/-   ##
==========================================
- Coverage   85.81%   85.81%   -0.01%     
==========================================
  Files        4459     4459              
  Lines      208966   208988      +22     
  Branches    39064    39063       -1     
==========================================
+ Hits       179329   179341      +12     
- Misses      26470    26480      +10     
  Partials     3167     3167              

Flag	Coverage Δ
dify-ui	93.27% <ø> (ø)
web	86.76% <83.95%> (-0.01%)	⬇️

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