Improve README discoverability

[he-chun]

Summary

• Rewrites the first screen around the local-first Zotero duplicate-prevention value proposition.
• Adds localized quick links, Quick start guidance, and Why use it scenarios.
• Adds five search-oriented FAQ entries, including the explicit non-plagiarism-checker boundary.
• Moves Release verification and unchanged SHA-256 checksums into localized disclosure sections.
• Keeps the support matrix factual and synchronized in English and Simplified Chinese.
• Updates the GitHub description and topics for project discoverability.

Verification

• npm ci
• npm test — 178 tests passed
• npm run check — 129 files checked

Scope

No product code, package version, tag, Release, Release asset, update manifest, changelog release content, or CI workflow changed.