Refactor wagon specifications to rely on wagon type; remove tare weight and max payload from wagon entity and related components

apps/edr-freight-web/backoffice/src/services/wagon.service.ts

@@ -15,14 +15,16 @@ export interface Wagon {
     label: string;
     country?: string;
   } | null;
+  /** Owns this wagon's spec — tare, capacity, length are read from here, never off the wagon. */
   wagonType?: {
     id: string;
     code: string;
     name: string;
     supportedLoadTypes?: string[];
+    tareWeightTons?: number;
+    capacityTons?: number;
+    lengthMeters?: number;
   } | null;
-  tareWeight: number;
-  maxPayloadWeight: number;
   status: Freight.WagonStatus;
   currentYardId: string | null;
   currentYard?: { id: string; label?: string; code?: string } | null;