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/api/src/routes/scans.rs

@@ -0,0 +1,49 @@
+use axum::Json;
+use axum::Router;
+use axum::extract::State;
+use axum::routing::post;
+use holzleitner_application::dto::{ApplyScansRequest, ApplyScansResponse};
+
+use crate::error::ApiError;
+use crate::extractors::AuthenticatedUser;
+use crate::state::AppState;
+
+pub fn router() -> Router<AppState> {
+    Router::new().route("/scans", post(apply_scans))
+}
+
+/// Wendet eine Liste von Scan-Events idempotent an.
+///
+/// Pro Event ein eigenes Resultat. Status `applied` schreibt einen
+/// frischen Audit-Eintrag, `duplicate` liefert den aktuellen Stand am
+/// Server, `rejected` enthält die Begründung. Reihenfolge der `results`
+/// entspricht der Reihenfolge der `scans` im Request.
+#[utoipa::path(
+    post,
+    path = "/scans",
+    tag = "scans",
+    request_body = ApplyScansRequest,
+    responses(
+        (status = 200, description = "Bulk-Ergebnis pro Event", body = ApplyScansResponse),
+        (status = 401, description = "Authentifizierung fehlgeschlagen")
+    ),
+    security(
+        ("bearer_auth" = [])
+    )
+)]
+pub async fn apply_scans(
+    State(state): State<AppState>,
+    AuthenticatedUser(claims): AuthenticatedUser,
+    Json(request): Json<ApplyScansRequest>,
+) -> Result<Json<ApplyScansResponse>, ApiError> {
+    tracing::info!(
+        actor = claims.personalnummer,
+        count = request.scans.len(),
+        "apply_scans",
+    );
+    let response = state
+        .apply_scans
+        .execute(request, claims.personalnummer)
+        .await?;
+    Ok(Json(response))
+}