Prepare 0.4.1 for the Chrome Web Store

[he-chun]

Summary

• add the maintainer-owned, provenance-documented extension icon and production icon declarations
• prepare bilingual Chrome Web Store listing, privacy, permission, reviewer, checklist, and promotional materials
• add three reviewed real 1280 x 800 English Chrome Web Store screenshots
• align the popup Not saved status color with the existing page badge blue
• prepare deterministic Paper Library Checker 0.4.1 candidate metadata and tests while keeping tracked updates.json on v0.4.0

Automated validation

• npm ci
• npm test (191/191)
• npm run check
• npm audit --audit-level=high --registry=https://registry.npmjs.org (0 vulnerabilities)
• npm run inventory:dependencies
• npm run build
• npm run inspect:artifacts
• candidate updates generation and validation
• Python and Windows archive validation
• CI Ubuntu/Windows byte-for-byte candidate comparison

Current local candidate SHA-256:

• XPI: 69857a35cf619f4fc7992c4b16d694894b1d7070f0806c06adc4506b0d5c9676
• Chrome ZIP: 1d72bdf7473486247511262433cf21d0aa1d34f63b0a6d985e797e175832cba3
• candidate updates manifest: 007c002428f423bf5e09cfff9d68efa8c39b7d3752d919250d93eb257a1cbaef

Ready gates

• dedicated-profile Zotero 9.0.x / Chrome 0.4.1 minimal smoke completed
• Zotero add-on 0.4.1, connection, index readiness, saved/not-saved checks, and Options connection test passed
• no unhandled error observed
• three real 1280 x 800 English screenshots added
• Simplified Chinese screenshots are an optional later localization enhancement, not an initial-submission blocker
• required CI and reproducibility checks passed

GitHub v0.4.1 and its reviewer XPI will be published after this PR merges. No Chrome Web Store upload, review submission, tag, or GitHub Release has been performed by this PR.