fix(web): align marketplace i18n terminology

[Jingyi-Dify]

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Summary

Fixes SNP-487

Linear issue: https://linear.app/dify/issue/SNP-487/onboarding-体验重构-marketplace-翻译检查

• Keep Marketplace untranslated and properly spaced in Simplified and Traditional Chinese copy.
• Align Marketplace page wording from plugins to integrations for the visible hero, tabs, and empty state.
• Keep Japanese Marketplace copy consistent with the 1.14 localization style while syncing the dataset-pipeline integration wording.

Screenshots

N/A. This PR only updates i18n copy.

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

Verification:

• Parsed all 19 changed i18n JSON files successfully.
• Verified 30 English visible Marketplace strings map to Chinese copy containing capitalized Marketplace with no CJK adjacency.
• Verified Japanese Marketplace copy has no remaining English Marketplace in the corresponding visible strings.
• Ran git diff --check.
• Pre-commit hook ran eslint --fix --pass-on-unpruned-suppressions on staged files.

From Codex

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.61%. Comparing base (50b3228) to head (352c2b6).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #37837   +/-   ##
=======================================
  Coverage   85.61%   85.61%           
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  Files        5032     5032           
  Lines      257481   257481           
  Branches    48888    48888           
=======================================
  Hits       220444   220444           
  Misses      32803    32803           
  Partials     4234     4234           

Flag	Coverage Δ
dify-ui	94.94% <ø> (ø)
web	85.63% <ø> (ø)

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