fix: add missing CreateCommentDto for ticket comments

src/ticket/dto/create-comment.dto.ts

@@ -0,0 +1,19 @@
+import {
+  IsString,
+  IsOptional,
+  IsArray,
+  MinLength,
+  MaxLength,
+} from 'class-validator';
+
+export class CreateCommentDto {
+  @IsString()
+  @MinLength(1)
+  @MaxLength(5000)
+  content: string;
+
+  @IsOptional()
+  @IsArray()
+  @IsString({ each: true })
+  files?: string[];
+}