- Extract phone validation to reusable utility (src/utils/phone-validation.ts) - Use libphonenumber-js for strict E.164 format validation - Normalize accepted numbers to canonical E.164 format - Add 22 comprehensive validation tests covering valid/invalid formats - Update existing tests to use valid E.164 test numbers - All 56 tests passing Co-Authored-By: Paperclip <noreply@paperclip.ing>