prices stored as float64 could lead to rounding errors when converting to cents for stripe (19.99 * 100 = 1998.99... truncating to 1998). canged Coffee.Price to int, storing cents directly. Updated the seed data, fallback products, API handlers, and all TUI display code to be in sync with this change.
feat: implement server-side cart persistence with Stripe PaymentIntents
Replaced the client-only in-mem cart with a database-backed cart system
- Add Cart and CartItem GORM models (two-table design)
- Add 6 cart API endpoints (get, set item, set address, set card, clear,
conver)
- Switch from Stripe Charge API to PaymentIntents with confirm:true
- Add 9 API client methods for cart and card operations
- Refactor TUI cart from map[int] (slice index) to map[uint] (CoffeeID)
- Replace single-shot checkout with saveCardAndConvert multi-step flow
- Add CheckingOut state with "submitting order..." processing indicator
- Fix Stripe tokenization to use secret key for server-side SSH apps
- Remove admin product CRUD endpoints and old checkout handler
