feat: add wagon usage computation and maintenance logging features

- Implemented  utility to calculate wagon usage metrics for train schedules.
- Created  for sending wagons to maintenance with optional notes.
- Added unit tests for train builder maintenance functionalities, including formatting train run labels and building maintenance notes.
- Developed  component for merging train schedules with detailed previews and reasons for merging.
- Introduced  component for selecting wagons with search functionality and selection limits.
- Created  for displaying and filtering audit logs, including detailed views of individual log entries.
- Added  for handling API interactions related to audit logs, including fetching logs and entity types.

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

@@ -0,0 +1,46 @@
+import { Controller, Get, Query } from '@nestjs/common';
+import { ApiBearerAuth, ApiOperation, ApiTags } from '@nestjs/swagger';
+import { PaginatedResponse } from '@edr/types';
+
+import { BookingStaff } from '../../common/booking-guards';
+import { FREIGHT_PERMS } from '../../seed/freight-permissions.registry';
+import { AuditService } from './audit.service';
+import { AuditLog } from './entities/audit-log.entity';
+import { AuditLogQueryDto } from './dto/audit-log-query.dto';
+
+/**
+ * Read-only view over the audit trail.
+ *
+ * Gated on `edr_freight_app:audit_log:view` — a dedicated view key rather than
+ * the broad `admin` key, so reading the trail can be granted without also
+ * granting write access to everything else.
+ *
+ * There is deliberately no write, update or delete endpoint here — rows are
+ * created only by `AuditInterceptor`, and an audit trail that can be edited
+ * through the API is not an audit trail.
+ */
+@ApiTags('audit')
+@ApiBearerAuth()
+@Controller('audit')
+export class AuditController {
+  constructor(private readonly auditService: AuditService) {}
+
+  @Get('logs')
+  @BookingStaff(FREIGHT_PERMS.auditLog.view)
+  @ApiOperation({
+    summary:
+      'List backoffice audit logs — filter by entity type, user, method, outcome and date range',
+  })
+  list(@Query() query: AuditLogQueryDto): Promise<PaginatedResponse<AuditLog>> {
+    return this.auditService.search(query);
+  }
+
+  @Get('types')
+  @BookingStaff(FREIGHT_PERMS.auditLog.view)
+  @ApiOperation({
+    summary: 'Distinct entity types present in the audit log (filter dropdown)',
+  })
+  types(): Promise<string[]> {
+    return this.auditService.listTypes();
+  }
+}