feat: definition of done per project

A project can ask that tickets reach a DONE status only with their
checklist ticked (settings.checklistBeforeDone, off by default; absent
when saving means unchanged). Members get a 422 telling how many steps are
left; owners and admins may still close it. Settings has the switch and
the ticket's checklist says when the project asks for it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/api/tracker/presenters/src/lib/http/dto/requests.dto.ts

@@ -318,6 +318,14 @@ export class ProjectSettingsBodyDto {
   @ValidateNested({ each: true })
   @Type(() => CustomFieldDefinitionBodyDto)
   customFields?: CustomFieldDefinitionBodyDto[];
+
+  @ApiPropertyOptional({
+    description:
+      'Definition of done: tickets reach a DONE status only with their checklist ticked (owners and admins may override). Absent: unchanged',
+  })
+  @IsOptional()
+  @IsBoolean()
+  checklistBeforeDone?: boolean;
 }
 
 export class AnalyticsQueryDto {