feat(train-scheduling): mid-route consist changes, audit history, safer workspace

- planned couples: loose wagons join the train at a route stop, added
  from the schedule yards tab; capacity credits them per corridor edge
  and coupling validates locomotive weight/length caps per leg
- real-cut toggle: a cut wagon permanently leaves the train build at
  its cut yard (soft cut still sits out one trip only)
- fix heaviest-leg display counting a shared slot's full cargo on
  every spanned edge (phantom pull-weight overload on S-2026-00045)
- confirmation dialogs for workspace add/load/unload/remove actions
- train-builder History and Detached-wagons tabs, backed by paginated
  endpoints; builder detaches now always write adjustment-log rows

Migrations 3660 (planned_wagon_couples, planned_wagon_real_cuts) and
3670 (adjustment log train_schedule_id nullable) — both applied to the
dev DB by hand; watch mode does not run migrations.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/edr-freight-api/src/modules/bookings/bookings.controller.ts

@@ -657,16 +657,18 @@ export class BookingsController {
   }
 
   @Post('wagon-cancellations/:cancellationId/withdraw')
-  @ApiOperation({ summary: 'Withdraw a fee-pending wagon cancellation (owner, or staff with the void permission)' })
+  @ApiOperation({ summary: 'Withdraw a fee-pending wagon cancellation — STAFF ONLY (void permission). A customer cancellation is final; only an admin can revert it.' })
   async withdrawWagonCancellation(
     @Param('cancellationId', ParseUUIDPipe) cancellationId: string,
     @CurrentUser() user: TCurrentUser,
   ) {
-    await this.assertWagonCancellationActor(
-      cancellationId,
-      user,
-      FREIGHT_PERMS.bookings.wagonCancellationVoid,
-    );
+    // Customer cancellations are irreversible from the portal — no owner
+    // fallback here. Only staff holding the void permission can revert one.
+    if (!hasFreightPermission(user, FREIGHT_PERMS.bookings.wagonCancellationVoid)) {
+      throw new ForbiddenException(
+        'A cancellation request cannot be withdrawn from the portal — contact EDR staff.',
+      );
+    }
     return this.wagonCancellationService.withdraw(cancellationId);
   }