feat: implement 20ft container weight-pairing validation

- Added ContainerValidationService to handle 20ft weight-pairing logic.
- Introduced validate20ftWeightPairing utility function to check weight differences.
- Updated BookingPricingService to include overweight line details and pairing errors in price response.
- Enhanced BookingTransitionService to reject submissions with unpairable 20ft containers.
- Created ShipmentValidation interface for pre-submit validation of container contracts.
- Integrated shipment validation into the contract booking process, providing warnings for overweight containers and hard blocks for pairing errors.
- Updated front-end components to display validation results and prevent submission when errors are present.

apps/edr-freight-api/src/modules/bookings/dto/generate-price-response.dto.ts

@@ -27,6 +27,20 @@ export class PriceLineItemDto {
   currency!: string;
 }
 
+export class OverweightLineDto {
+  @ApiProperty()
+  containerTypeCode!: string;
+
+  @ApiProperty()
+  totalVgmTons!: number;
+
+  @ApiProperty()
+  maxAllowedTons!: number;
+
+  @ApiProperty()
+  excessTons!: number;
+}
+
 export class GeneratePriceResponseDto {
   @ApiProperty()
   bookingId!: string;
@@ -42,4 +56,16 @@ export class GeneratePriceResponseDto {
 
   @ApiProperty({ type: [String] })
   warnings!: string[];
+
+  /** Overweight container lines (VGM over the weight-limit rule) — surcharge already in lineItems. */
+  @ApiProperty({ type: [OverweightLineDto] })
+  overweightLines!: OverweightLineDto[];
+
+  /**
+   * 20ft weight-pairing violations. Non-empty means the booking cannot be
+   * balanced onto wagons and submit is HARD-BLOCKED — the customer must fix
+   * container weights/quantities. (Overweight, by contrast, only warns.)
+   */
+  @ApiProperty({ type: [String] })
+  pairingErrors!: string[];
 }