fix(web): use buttons for pricing categories

[lyzno1]

Summary

• replace the cloud/self-hosted pricing category containers with native buttons
• expose the active category through aria-pressed
• verify both accessible category names, initial state, Space-key activation, and the full pricing-list transition
• migrate the remaining category-switching tests from text nodes to semantic buttons
• remove the two exact jsx-a11y suppressions

Boundary

• limited to the pricing category Tab owner, its existing integration test, and the suppression baseline
• plan pricing, yearly billing, payment flows, category state, and custom SVG assets are unchanged
• no CSS-icon or React component cleanup is mixed into this PR

Validation

• regression proof: 5 of 20 integration tests fail against the old non-semantic category controls
• pnpm --dir web exec vp test run __tests__/billing/pricing-modal-flow.test.tsx — 20/20 passed
• ./node_modules/.bin/vp lint web/app/components/billing/pricing/plan-switcher/tab.tsx web/__tests__/billing/pricing-modal-flow.test.tsx
• pnpm --dir web lint:a11y app/components/billing/pricing/plan-switcher/tab.tsx
• pnpm check — 0 errors, 2059 existing warnings
• git diff --check

Visual regression review

• verify cloud and self-hosted controls retain their horizontal padding, vertical padding, gap, SVG alignment, typography, and active/inactive colors
• appearance-none prevents platform button chrome; the explicit flex centering matches the previous containers
• verify the pricing header height and divider alignment do not move
• the only intended new visual state is the keyboard-only focus-visible ring

Stack

Independent root PR based directly on current origin/main; no child cleanup is required.

Rollback

Revert commit 19415761dc; no other accessibility PR depends on this branch.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.43%. Comparing base (7522ae1) to head (e4fa311).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #40360      +/-   ##
==========================================
- Coverage   86.47%   86.43%   -0.05%     
==========================================
  Files        5264     5107     -157     
  Lines      294867   290740    -4127     
  Branches    59029    57924    -1105     
==========================================
- Hits       254976   251288    -3688     
+ Misses      34950    34511     -439     
  Partials     4941     4941              

Flag	Coverage Δ
cli	?
dify-ui	93.49% <ø> (ø)
web	86.11% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.