Enatega Admin-Dashboard + Customer: Ensure Consistent Naming for "Voucher" and "Coupons"

### Issue:
The terms "Voucher" and "Coupons" are used interchangeably in the system, leading to inconsistency and potential confusion for users.

### Impact:

Users may not clearly understand whether "Voucher" and "Coupons" refer to the same feature or different functionalities.
Inconsistent naming can create confusion in the UI, documentation, and communication.
It may affect API responses, database fields, or reports if both terms are used inconsistently in different places.

### Recommendation:

Choose a single, consistent term: either "Voucher" or "Coupon."
Update all instances of the term across the UI, API, documentation, and database schema.
Ensure consistency in user-facing messages, buttons, forms, and reports.
Communicate the change to relevant teams to maintain uniformity in future development.

Search the Admin Dashboard and Customer UI, API responses, documentation, database schema, reports, messages, buttons, and forms for uses of "Voucher" and "Coupons." First determine which single term the project will adopt, then inventory every affected location and verify that the chosen term is consistent across all listed surfaces.

Written by the indexing model from the issue text.