New router: routers/coupons.py
Admin endpoints:
- GET /api/coupons - List all coupons with stats
- POST /api/coupons - Create new coupon
- PUT /api/coupons/{id} - Update coupon
- DELETE /api/coupons/{id} - Soft-delete (set active=false)
- GET /api/coupons/{id}/redemptions - Redemption history
User endpoints:
- POST /api/coupons/redeem - Redeem coupon code
Features:
- Three coupon types: single_use, period, wellpass
- Wellpass logic: Pauses existing personal grants, resumes after expiry
- Max redemptions limit (NULL = unlimited)
- Validity period checks
- Activity logging
- Duplicate redemption prevention
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
