Address validation provides clear error messages

A generic "Validation failed" toast on submit tells the shopper nothing about which of the twelve fields is wrong. They scroll, squint, guess, retry, and leave. Field-specific inline errors — surfaced on blur next to the offending input — turn a recovery into a three-second fix. Screen-reader users are hit hardest: a toast with no aria-live region and no role="alert" on the field error is invisible to them, excluding customers who rely on assistive tech.

Validate on onBlur per field and render a role="alert" span next to the input when validation fails. Write messages that name the rule ("Zip code must be 5 or 9 digits"), not the status ("Invalid"). Place this in src/components/AddressForm.tsx.

if (!/^\d{5}(-\d{4})?$/.test(zip)) return { zip: 'Zip code must be 5 or 9 digits (e.g., 90210)' }
{errors.zip && <span role="alert">{errors.zip}</span>}