feat: Implement GitHub Issues-based lesson feedback system (#29)

[brainstrom286]

Add GitHub Issues-based Lesson Feedback

This PR adds an inline lesson feedback system using the GitHub Issues API.

What’s included

• New server-side API route (/api/feedback) to create GitHub issues securely
• Inline feedback form added to lesson cards (no external redirect)
• Automatic labeling (lesson-feedback, bug, suggestion, content-quality)
• Basic spam protection (rate limiting + minimum description length)
• Proper success/error handling

Notes

• API route is server-rendered (prerender = false)
• GitHub token will be provided via org secrets in production

Closes #29

[github-actions]

❌ PR checks failed

One or more validation checks failed. Please review the workflow logs to see what went wrong.

Common issues:

• 📊 Data validation: Google Sheets CSV is unreachable or has invalid data
• 🔍 TypeScript check: Type errors in code
• 🏗️ Build: Build process failed
• 📄 Critical pages: Missing required pages (index, lessons, pathways)
• 🔗 Internal links: Broken links detected

[brainstrom286]

Noted the GitHub Actions checks.
@jt14den happy to address any issues related to this PR if changes are needed.