feat(bookings): add ad-hoc additional-charge module

New freight.additional_charge table, independent of BookingClearanceCharge
(unbounded per booking, free-text reason). Draft -> send issues an invoice
and notifies the customer in-app/SMS/email; settles via the standard
.invoice.paid event. Adds the Additional charges row-menu entry
next to Cancel booking, permission-gated.

Not included: the Additional Payments tab UI, add-charge modal, portal pay
flow.

apps/edr-freight-api/src/modules/bookings/dto/additional-charge.dto.ts

@@ -0,0 +1,35 @@
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
+import { Type } from 'class-transformer';
+import { IsIn, IsNumber, IsOptional, IsPositive, IsString, Length } from 'class-validator';
+
+export class CreateAdditionalChargeDto {
+  @ApiProperty({ example: 'Re-weighing fee at Mojo dry port' })
+  @IsString()
+  @Length(1, 2000)
+  reason!: string;
+
+  @ApiProperty({ example: 4500 })
+  @Type(() => Number)
+  @IsNumber()
+  @IsPositive()
+  amount!: number;
+
+  @ApiProperty({ example: 'ETB' })
+  @IsString()
+  @Length(3, 8)
+  currency!: string;
+
+  /** 'send' issues the invoice + notifies the customer immediately; omit/'draft' just saves it. */
+  @ApiPropertyOptional({ enum: ['draft', 'send'], default: 'draft' })
+  @IsOptional()
+  @IsIn(['draft', 'send'])
+  action?: 'draft' | 'send';
+}
+
+export class CancelAdditionalChargeDto {
+  @ApiPropertyOptional({ example: 'Raised in error' })
+  @IsOptional()
+  @IsString()
+  @Length(1, 2000)
+  reason?: string;
+}