- Add FlyerSession, FlyerItem, and FlyerSelection models to Prisma schema
- Implement session persistence with weekly key generation in FlyerImportService
- Add FlyerSelectionModule to AppModule
- Extend FlyerImportResponse with sessionId and flyerItemId fields
- Create new flyer-selection module directory structure
- Add migration for flyer session and selection tables
BREAKING CHANGE: Flyer import now persists data to FlyerSession and FlyerItem tables