fix(web): align web app nav item width

[lyzno1]

Summary

• Restores the Web Apps section content padding to px-2 so installed app rows align with the main nav item track.
• Keeps the fix scoped to the Web Apps list and leaves the default ScrollArea scrollbar styling unchanged.

Regression Source

• Introduced by 9d3ac1b7b32c074889b36f0d96dd1ed6dde6fe5b (fix: simplify scroll area composition (#38113)), which changed ScrollAreaContent in web-apps-section.tsx from px-2 to pr-5 pl-2.
• In the 240px main sidebar, that reduced the row track from 240 - 8 - 8 = 224px to 240 - 8 - 20 = 212px, making Web App items narrower than the Figma nav shell design.

Tests

• pnpm -C web exec eslint app/components/main-nav/components/web-apps-section.tsx
• git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.33%. Comparing base (d2216fe) to head (3fda8fd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #38146   +/-   ##
=======================================
  Coverage   85.33%   85.33%           
=======================================
  Files        4964     4964           
  Lines      258334   258334           
  Branches    49023    49023           
=======================================
  Hits       220452   220452           
  Misses      33593    33593           
  Partials     4289     4289           

Flag	Coverage Δ
dify-ui	94.93% <ø> (ø)
web	85.02% <ø> (ø)

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