F4: add explicit inspection cancellation DTO

api-v3/src/inspection-visits/dto/cancel-inspection-visit.dto.ts

@@ -0,0 +1,10 @@
+import { Transform } from 'class-transformer';
+import { IsString, MaxLength, MinLength } from 'class-validator';
+
+export class CancelInspectionVisitDto {
+  @Transform(({ value }) => typeof value === 'string' ? value.trim() : value)
+  @IsString()
+  @MinLength(10)
+  @MaxLength(4000)
+  reason!: string;
+}