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/web/tracker/domain/src/lib/models/workflow.ts

@@ -97,6 +97,8 @@ export interface ProjectSettings {
   issueTypes: IssueTypeOption[];
   areas: AreaOption[];
   customFields: CustomFieldDefinition[];
+  /** Definition of done: a DONE status only with the checklist ticked. */
+  checklistBeforeDone?: boolean;
 }
 
 export const FINISHED_CATEGORIES: readonly StatusCategory[] = [