refactor: enhance layout and scrolling behavior in various modals for improved user experience

[CodingOnStar]

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Summary

refactor: enhance layout and scrolling behavior in various modals for improved user experience

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.94%. Comparing base (28153df) to head (39ef2d9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #36210      +/-   ##
==========================================
- Coverage   85.94%   85.94%   -0.01%     
==========================================
  Files        4454     4454              
  Lines      210917   210911       -6     
  Branches    39427    39426       -1     
==========================================
- Hits       181272   181266       -6     
  Misses      26442    26442              
  Partials     3203     3203              

Flag	Coverage Δ
dify-ui	94.40% <ø> (ø)
web	86.60% <100.00%> (-0.01%)	⬇️

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