feat(last-mile): default the approval advance to the live rate

The chief's typed advance was mandatory, so the rule-based estimate shown in
the approve dialog had to be retyped and could silently diverge from it.

advanceAmount is now optional: the advance defaults to the live last-mile
rate estimate (km x rate) and the typed value is only an override. When no
rate covers the job the request is rejected with a message telling the chief
to enter the amount manually, rather than approving a zero advance.

The advance invoice now bills in the rate's currency from the snapshotted
contract summary, falling back to the booking payment currency only when the
amount came from a manual override.

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

apps/edr-freight-api/src/modules/last-mile-requests/dto/approve-last-mile-request.dto.ts

@@ -1,13 +1,19 @@
-import { ApiProperty } from '@nestjs/swagger';
+import { ApiPropertyOptional } from '@nestjs/swagger';
 import { Transform } from 'class-transformer';
-import { IsNumber, Min } from 'class-validator';
+import { IsNumber, IsOptional, Min } from 'class-validator';
 
 export class ApproveLastMileRequestDto {
-  // The approve dialog prefills this from GET :id/price-estimate (rule-based),
-  // but the chief can still override — the typed value is what's invoiced.
-  @ApiProperty({ description: 'Advance amount the customer must pay before execution proceeds', example: 3000 })
-  @Transform(({ value }) => Number(value))
+  // Omitted = the rule-based last-mile rate estimate is the advance. The chief
+  // can still override with an explicit amount (required when no rate covers
+  // the job).
+  @ApiPropertyOptional({
+    description:
+      'Advance override. Omitted = the amount comes from the live last-mile rates (km × rate).',
+    example: 3000,
+  })
+  @IsOptional()
+  @Transform(({ value }) => (value === null || value === undefined || value === '' ? undefined : Number(value)))
   @IsNumber()
   @Min(0.01)
-  advanceAmount!: number;
+  advanceAmount?: number;
 }

apps/edr-freight-api/src/modules/last-mile-requests/last-mile-requests.controller.ts

@@ -110,7 +110,7 @@ export class LastMileRequestsController {
 
   @Post(':id/approve')
   @BookingStaff(FREIGHT_PERMS.lastMile.requestApprove)
-  @ApiOperation({ summary: 'Truck & Machinery chief approves the request — LM contract becomes signable; the advance invoice follows the customer signature' })
+  @ApiOperation({ summary: 'Truck & Machinery chief approves the request — the advance defaults to the live last-mile rate; LM contract becomes signable and the advance invoice follows the customer signature' })
   approve(
     @Param('id', ParseUUIDPipe) id: string,
     @Body() dto: ApproveLastMileRequestDto,

apps/edr-freight-api/src/modules/last-mile-requests/last-mile-requests.service.ts

@@ -299,7 +299,11 @@ export class LastMileRequestsService {
     return this.findById(id);
   }
 
-  async approve(id: string, staffId: string | null, advanceAmount: number): Promise<LastMileRequest> {
+  async approve(
+    id: string,
+    staffId: string | null,
+    advanceOverride?: number | null,
+  ): Promise<LastMileRequest> {
     const request = await this.findById(id);
     if (request.status !== LastMileRequestStatus.Submitted) {
       throw new BadRequestException(`Only a submitted request can be approved (current status: ${request.status})`);
@@ -307,6 +311,18 @@ export class LastMileRequestsService {
     const booking = request.booking ?? (await this.bookingsRepository.findById(request.bookingId));
     if (!booking) throw new NotFoundException(`Booking ${request.bookingId} not found`);
 
+    // The live last-mile rates are the authority on the advance (km × rate);
+    // the chief's typed amount is only an override — and the only path when no
+    // rate covers the job. Snapshotted so the contract and invoice stay immune
+    // to later rate edits.
+    const estimate = await this.priceEstimate(id);
+    const advanceAmount = advanceOverride ?? estimate.total;
+    if (!advanceAmount || advanceAmount <= 0) {
+      throw new BadRequestException(
+        'No live last-mile rate covers this job — enter the advance amount manually.',
+      );
+    }
+
     // Idempotent per booking — reuses the record if one already exists.
     const lastMile = await this.lastMileService.create({
       bookingId: request.bookingId,
@@ -316,10 +332,6 @@ export class LastMileRequestsService {
 
     // No invoice yet: the advance is invoiced by LastMileContractService.sign()
     // once the customer has signed the LM contract — doc first, then payment.
-    // Snapshot the rate estimate now so the contract shows the numbers the
-    // chief actually approved against, immune to later rate edits.
-    const estimate = await this.priceEstimate(id);
-
     await this.requestsRepository.update(id, {
       status: LastMileRequestStatus.Approved,
       reviewedByStaffId: staffId,
@@ -364,7 +376,10 @@ export class LastMileRequestsService {
       type: 'LAST_MILE_ADVANCE',
       companyId: booking.companyId,
       companyProfileId: booking.companyProfileId || '',
-      currency: booking.paymentCurrency || 'ETB',
+      // The advance is priced by the last-mile rate, so it bills in that
+      // rate's currency (birr for domestic trucking) — the booking's payment
+      // currency is only the fallback when the amount was a manual override.
+      currency: request.contractSummary?.currency || booking.paymentCurrency || 'ETB',
       lines: [
         {
           chargeType: 'LAST_MILE_ADVANCE',