Set Start/end time & date on coupons

🔍 Problem Statement

Coupons can only be configured with a start date and end date at the date level — there is no option to set a specific start or end time. This prevents precise promotional windows (e.g. flash sales that end at midnight) and forces publishers to manually activate/deactivate coupons.

💡 User Story

As a Pelcro admin, I want to set start and end times (not just dates) on coupons, so that I can run time-precise promotions like flash sales without manual activation.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given a coupon configuration, when an admin sets a start and end datetime (including time), then the coupon activates and deactivates at the exact specified times.