Introduce Zip Code Validations on checkout

Problem Statement

Currently, there is no ZIP code validation step within Pelcro prior to a user selecting a print subscription plan. This means users in areas where print fulfillment is not available may proceed through the checkout flow, leading to unfulfillable orders and a poor user experience.

User Story

As a platform operator, I want to restrict checkout for print plans to users with specific ZIP codes, so that only users in serviceable areas can purchase print subscriptions.

Definition of Done

1. Add ZIP code restriction settings at the plan/product level

2. Array of zip codes should be enabled

3. Only users whose address matches an allowed ZIP code should be able to purchase the restricted plan

4. Users with non-matching ZIP codes should see a clear message explaining that print delivery is not available in their area

5. Validations should be applied similar to country validations in the platform/checkout.