Initial: Rust-Backend mit Clean Architecture (domain/application/infrastructure/api)

Vier-Crate-Workspace mit:
- Domain: Account, Car, Tour, Delivery, DeliveryItem, DeliveryNote, Customer,
  Article, Warehouse, ScanState, AuditAction — alle mit serde + feature-gated
  utoipa::ToSchema.
- Application: Ports (TourRepository, DeliveryRepository, ScanRepository,
  DeliveryNoteRepository, CarRepository, AuthService) und Use Cases.
- Infrastructure: Postgres-Adapter via sqlx (PgTourRepository etc.) +
  Keycloak-AuthService mit JWKS-Cache + OIDC-Discovery.
- API: Axum 0.8, utoipa-OpenAPI + Swagger-UI, JWT-Bearer-Middleware,
  AuthenticatedUser-Extractor.

Endpoints:
- GET /me/tours/today, /tours/{id}, /accounts/{pn}, /me/cars, /health
- POST /sync/tour, /scans (bulk + idempotent via clientScanId),
  /deliveries/{id}/{hold,resume,cancel,complete,notes}, /me/cars
- PUT /tours/{id}/delivery-order, /deliveries/{id}/assigned-car, /me/cars/{id}
- PATCH /me/cars/{id}

Datenmodell:
- 6 Migrationen (accounts, tours/deliveries/items + Stammdaten,
  scan_audit mit clientScanId-UNIQUE, state_reason refactor,
  delivery_notes, cars + FKs nachziehen).
- Business-stabile Beleg-Keys (belegart_id, belegnummer) für ERP-Sync.
- Append-only scan_audit + embedded scan_state als doppelte Wahrheit.

Dev-Setup:
- docker-compose mit Postgres 17 + Keycloak 26
- Keycloak-Realm 'holzleitner' mit Public-Client (PKCE), Testfahrer
  (PN 1001) + Audience-/Personalnummer-Mapper

crates/application/src/usecases/mod.rs

@@ -0,0 +1,28 @@
+//! Use Cases — Geschäftslogik-Operationen.
+//!
+//! Jeder Use Case kapselt **eine** Operation aus Sicht des Anwenders
+//! (z. B. „Tour des Tages laden", „Artikel scannen", „Lieferung
+//! abbrechen"). Use Cases nehmen Ports (Trait-Objekte) per Konstruktor
+//! entgegen und orchestrieren damit das Domänenmodell.
+
+pub mod apply_delivery_action;
+pub mod apply_scans;
+pub mod cars;
+pub mod create_delivery_note;
+pub mod get_account;
+pub mod get_tour;
+pub mod list_my_tours_today;
+pub mod set_delivery_order;
+pub mod sync_tour;
+
+pub use apply_delivery_action::ApplyDeliveryActionUseCase;
+pub use apply_scans::ApplyScansUseCase;
+pub use cars::{
+    AssignCarToDeliveryUseCase, CreateMyCarUseCase, ListMyCarsUseCase, UpdateMyCarUseCase,
+};
+pub use create_delivery_note::CreateDeliveryNoteUseCase;
+pub use get_account::GetAccountUseCase;
+pub use get_tour::GetTourUseCase;
+pub use list_my_tours_today::ListMyToursTodayUseCase;
+pub use set_delivery_order::SetDeliveryOrderUseCase;
+pub use sync_tour::SyncTourUseCase;