feat(warehouses): backoffice UI for container stack positions

Surfaces the physical stack/slot model in the staff app.

- ZoneLayoutModal: stacks drawn level by level with occupancy colours,
  configured-vs-built-vs-occupied counts, and stack create/delete plus
  block/reserve/free on empty levels
- SlotPicker in the store and move modals, offering only the next
  fillable level of each stack so the form cannot suggest a position
  the API will refuse
- move modal warns when a container is buried, lists the blockers, and
  disables the action instead of firing a 409
- fix: move() now asserts accessibility server-side, matching release —
  both are exits from a stack

apps/edr-freight-api/src/modules/bookings/booking-wagon-cancellation.service.ts

@@ -1875,9 +1875,12 @@ export class BookingWagonCancellationService {
           // the same cargo); number/seal/VGM come from the override when given.
           units: sized.map((u, i) => ({
             containerNumber: replacement?.[i]?.containerNumber ?? u.containerNumber,
+            // A credit snapshot taken before seals were mandatory can carry
+            // none; the booking service normalizes the blank back to null
+            // rather than blocking the rebook of already-paid cargo.
             sealNumber: replacement
-              ? (replacement[i]?.sealNumber ?? undefined)
-              : (u.sealNumber ?? undefined),
+              ? (replacement[i]?.sealNumber ?? '')
+              : (u.sealNumber ?? ''),
             vgmTons: replacement?.[i]?.vgmTons ?? u.vgmTons,
             isHazardous: u.isHazardous,
             isReefer: u.isReefer,

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

@@ -2250,7 +2250,9 @@ export class ContractBookingService {
           unitRepo.create({
             bookingContainerId: containerRow.id,
             containerNumber: unit.containerNumber,
-            sealNumber: unit.sealNumber ?? null,
+            // Legacy units recovered by the remainder placement can still
+            // arrive sealless — keep those null rather than empty-string.
+            sealNumber: unit.sealNumber?.trim() || null,
             vgmTons: unit.vgmTons,
             isHazardous: unit.isHazardous ?? false,
             isReefer: unit.isReefer ?? false,

apps/edr-freight-api/src/modules/contracts/dto/create-booking-under-contract.dto.ts

@@ -7,6 +7,7 @@ import {
   IsEmail,
   IsIn,
   IsInt,
+  IsNotEmpty,
   IsNumber,
   IsOptional,
   IsString,
@@ -32,10 +33,12 @@ export class CreateContainerUnitDto {
   })
   containerNumber!: string;
 
-  @ApiPropertyOptional()
-  @IsOptional()
+  @ApiProperty({ description: 'Seal number — required on every container, import and export alike.' })
   @IsString()
-  sealNumber?: string;
+  @Transform(({ value }) => (typeof value === 'string' ? value.trim() : value))
+  @IsNotEmpty({ message: 'sealNumber is required' })
+  @MaxLength(64)
+  sealNumber!: string;
 
   @ApiProperty({ description: 'VGM in tons', minimum: 0 })
   @IsNumber()

apps/edr-freight-api/src/modules/train-scheduling/remainder-placement.service.ts

@@ -333,7 +333,9 @@ export class RemainderPlacementService {
 
     return deferred.map((u) => ({
       containerNumber: u.containerNumber,
-      sealNumber: u.sealNumber ?? undefined,
+      // Deferred units predate the seal requirement; the booking service
+      // normalizes the blank back to null rather than rejecting the re-book.
+      sealNumber: u.sealNumber ?? '',
       vgmTons: Number(u.vgmTons),
       isHazardous: u.isHazardous,
       isReefer: u.isReefer,

apps/edr-freight-api/src/modules/warehouses/warehouse-inventory.service.ts

@@ -3140,6 +3140,13 @@ export class WarehouseInventoryService {
 
       const { warehouse, yard, zone } = await this.validateLocation(manager, dto);
 
+      // Taking a box out of a stack is physically impossible while others stand
+      // on top of it — the same rule the release path enforces. Moving is one of
+      // those exits, so it is checked here rather than only at release.
+      if (item.slotId) {
+        await this.placement.assertAccessible(item.id, manager);
+      }
+
       // A move that names a slot is validated against the hierarchy it claims;
       // one that does not clears the old slot, because the box has left it.
       if (dto.slotId) {