- Fix HTML injection vulnerability with proper entity encoding
- Fix rate limit cleanup bug (count vs timestamp confusion)
- Add URL validation to prevent open redirect attacks
- Add expiration to in-memory deduplication entries
- Use Zod schema for config validation
- Add email format validation
All 29 tests passing. Ready for Code Reviewer final review.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
