Add time-bounded percentage discounts with per-tariff overrides
and countdown timer support for landing pages.
- Add 5 discount columns to LandingPage model (percent, overrides,
starts_at, ends_at, badge_text) with Alembic migrations 0027-0028
- Add DB CHECK constraints for discount_percent range and date ordering
- Add discount price calculation in validate_and_calculate() and
public landing config endpoint with consistent formula
- Add admin CRUD with Pydantic validation, cascade-clear on removal,
merged date validation on partial updates, size bounds
- Remove discount_overrides from public API (baked into prices)
- Add size limits for allowed_tariff_ids and allowed_periods
Fringg
aa7d98630d