Nine SQLModel table models covering the Organization/Route hierarchy
(WineCategory, Organization, User, Route, Participant, PurchaseRound,
WineOffering, Order, OrderLine), with explicit tablenames, FK cascade
behavior, and a CHECK constraint preventing a PurchaseRound from
reaching open/closed status without its opens_at/order_deadline_at/
pickup_at dates set. Also fixes the Alembic script template to import
sqlmodel (needed for autogenerate's AutoString column type).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
