Card holder name accepted digits/slashes and whitespace-only input could be saved across billing address, shipping address and update account. Migrate all three to react-hook-form + zod (mirroring signup-form.tsx), trimming and validating each field before save and surfacing inline errors, and cap address at 300 characters to match the backend DTO limit.
Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com