Model order attributes as configurable fields on the order (Field UI, Views, form capture, field-backed matchers)

Model order attributes as configurable fields on the order (yoyaku_transaction) entity, so a site defines what it captures and counts bookings by, with typed fields that are Views columns with no custom code.

• Enable Field UI on the order; ship booker_email and booker_name as base attribute fields; any field an administrator adds participates by convention.
• Field-backed attribute matcher, derived one per attribute field, replacing the hardcoded email matcher; value, match and capture all go through the field API.
• Generalize the webform booking handler to map submission elements onto order attributes; enforcement then runs over every captured dimension.
• Rename the customer fields and terminology to booker (pre-1.0, no update hooks).
• Example module: a birth date element mapped to a configurable date field, plus a minimum-age (18+) order constraint reading it.

Documentation and French translations are updated. Kernel tests cover the field-backed matcher, an administrator-added field used as a matcher, and the card-token dimension.