update joins in repository services to use entity classes and enhance booking form with hazardous/reefer toggles

apps/edr-freight-api/src/modules/contracts/contract-booking.service.ts

@@ -138,6 +138,11 @@ export class ContractBookingService {
     // no override. Checked before any row is written.
     if (freightType === 'CONTAINER') {
       await this.assertWithinMaxCapacity(contract, dto);
+      // 20ft weight-pairing gate at CREATION: two 20ft on a wagon must differ
+      // ≤ the cap, and drawdown bookings never pass through submit — so this is
+      // their only chance to hard-block an unbalanceable set. Entry order is
+      // irrelevant (the check sorts by weight before pairing).
+      await this.assert20ftPairableAtCreate(dto);
     }
 
     // Denormalize route/direction/freight onto the booking for the scheduling engine.
@@ -761,6 +766,35 @@ export class ContractBookingService {
     }
   }
 
+  /**
+   * Hard-block booking creation when the 20ft container weights cannot be
+   * balanced onto wagons (pair diff over the global cap). Same rule the
+   * shipment-form preview reports as `pairingErrors`, enforced server-side.
+   */
+  private async assert20ftPairableAtCreate(
+    dto: CreateBookingUnderContractDto,
+  ): Promise<void> {
+    const twentyFtUnits = (dto.containers ?? [])
+      .filter((line) => (line.containerSize ?? '').includes('20'))
+      .flatMap((line, lineIdx) =>
+        (line.units ?? []).map((u, idx) => ({
+          label: u.containerNumber || `20ft-${lineIdx + 1}.${idx + 1}`,
+          grossWeightTons: Number(u.vgmTons ?? 0),
+        })),
+      );
+    if (twentyFtUnits.length < 2) return;
+
+    const maxDiff = await this.max20ftPairDiffTons();
+    const violations = validate20ftWeightPairing(twentyFtUnits, maxDiff);
+    if (violations.length) {
+      throw new BadRequestException(
+        `Cannot create booking — 20ft containers cannot be paired on wagons: ${violations
+          .map((v) => v.message)
+          .join(' ')}`,
+      );
+    }
+  }
+
   private async max20ftPairDiffTons(): Promise<number> {
     const row = await this.dataSource
       .getRepository(TrainSchedulingGlobalRules)