[codex] fix project card link structure

[Sean-Kenneth-Doherty]

Summary

• replace the whole-card project anchor with a dedicated Go to Project anchor so issue links are no longer nested inside another link
• keep the project-list filter script reading the project URL from the new CTA link, with a data-project-link fallback
• add rel="noopener noreferrer" to project and issue links that open in a new tab

Fixes #535.
Addresses #561 and #347.

Validation

• git diff --check main...HEAD
• pnpm build
• inspected built dist/index.html: max anchor depth is 1, no nested anchors, 152 project CTA links render, 9 issue links render, and all 168 target="_blank" anchors include rel="noopener noreferrer"
• inspected built script: it reads .Card-Link, no longer reads .Card-Real-Link, and keeps the data-project-link fallback

[Sean-Kenneth-Doherty]

Moved out of draft after local validation:

• pnpm build
• git diff --check
• Source scan of src/public found all target="_blank" anchors already include rel="noopener noreferrer".
• Built HTML scan of dist/index.html and dist/contribute-to-opensource/index.html found no blank-target anchors missing rel="noopener noreferrer".