feat: custom fields per project

Text, number, date or option-list fields defined in the project settings
(archived, never removed; their type is fixed once saved). Tickets hold
them, edited in the side panel, listed under the title and filtered by
option in the list view; also over GraphQL, REST (?field=ID:value) and MCP.

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

libs/api/tracker/application/src/lib/event-handlers/activity-summary.ts

@@ -90,6 +90,7 @@ const FIELD: Record<string, string> = {
   storyPoints: 'los puntos',
   startDate: 'la fecha de inicio',
   dueDate: 'la fecha límite',
+  customFields: 'los campos personalizados',
 };
 
 const list = (items: string[]) =>