refactor(web): migrate subscription create modal to dialog

[lyzno1]

Summary

• migrate the trigger subscription create modal from the legacy base Modal to @langgenius/dify-ui/dialog
• preserve the existing modal layout, sizing, disabled state, footer actions, and encrypted bottom slot behavior
• remove the unit test mock for the legacy base modal

Tests

• pnpm eslint app/components/plugins/plugin-detail-panel/subscription-list/create/common-modal.tsx app/components/plugins/plugin-detail-panel/subscription-list/create/tests/common-modal.spec.tsx --fix --quiet
• pnpm test app/components/plugins/plugin-detail-panel/subscription-list/create/tests/common-modal.spec.tsx

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.68%. Comparing base (fe2f7a8) to head (8766b36).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #35721   +/-   ##
=======================================
  Coverage   85.68%   85.68%           
=======================================
  Files        4459     4459           
  Lines      209085   209088    +3     
  Branches    39107    39110    +3     
=======================================
+ Hits       179149   179155    +6     
+ Misses      26769    26766    -3     
  Partials     3167     3167           

Flag	Coverage Δ
dify-ui	93.01% <ø> (ø)
web	86.49% <100.00%> (+<0.01%)	⬆️

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