implement update train details feature: add DTO, service method, and UI modal for editing train name and run numbers

apps/edr-freight-api/src/modules/trains/dto/update-train-details.dto.ts

@@ -0,0 +1,29 @@
+import { ApiPropertyOptional } from '@nestjs/swagger';
+import { IsNotEmpty, IsOptional, IsString, MaxLength } from 'class-validator';
+
+/**
+ * Edit a built train's display identity: its name and its fixed import/export
+ * run numbers. Composition (yard, locomotives, wagons) has its own endpoints.
+ * Omitted fields keep their current value; an empty trainName clears the name.
+ */
+export class UpdateTrainDetailsDto {
+  @ApiPropertyOptional({ description: 'Display name; empty string clears it' })
+  @IsOptional()
+  @IsString()
+  @MaxLength(100)
+  trainName?: string;
+
+  @ApiPropertyOptional({ description: 'Fixed IMPORT (even) run number' })
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(20)
+  importTrainNumber?: string;
+
+  @ApiPropertyOptional({ description: 'Fixed EXPORT (odd) run number' })
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(20)
+  exportTrainNumber?: string;
+}