fix(dify-ui): standardize story focus indicators

[lyzno1]

Summary

• Standardize story-local raw triggers, buttons, and links on Dify token focus rings instead of browser/default outline styles.
• Align raw dialog/popover inputs with Dify input focus treatment.
• Remove the unused ScrollArea AppSidebar story instead of carrying a local focus-style fix for it.

Validation

• pnpm -C packages/dify-ui exec eslint src/alert-dialog/index.stories.tsx src/dialog/index.stories.tsx src/popover/index.stories.tsx src/dropdown-menu/index.stories.tsx src/context-menu/index.stories.tsx src/tooltip/index.stories.tsx src/preview-card/index.stories.tsx src/toast/index.stories.tsx src/kbd/index.stories.tsx src/switch/index.stories.tsx src/radio-group/index.stories.tsx src/collapsible/index.stories.tsx src/scroll-area/index.stories.tsx
• pnpm -C packages/dify-ui type-check
• git diff --check

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.30%. Comparing base (a0f8347) to head (cc839ac).

Files with missing lines	Patch %	Lines
packages/dify-ui/src/dialog/index.tsx	71.42%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #38417   +/-   ##
=======================================
  Coverage   85.30%   85.30%           
=======================================
  Files        4995     4995           
  Lines      264319   264326    +7     
  Branches    50141    50141           
=======================================
+ Hits       225473   225479    +6     
- Misses      34428    34429    +1     
  Partials     4418     4418           

Flag	Coverage Δ
dify-ui	94.75% <71.42%> (-0.18%)	⬇️
web	84.86% <ø> (+<0.01%)	⬆️

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