feat: add pinned tag functionality and UI enhancements

- Introduced `isPinned` property to the `Tag` model for marking main objectives.
- Updated `TagForm` to include a checkbox for setting tags as pinned, enhancing user interaction.
- Enhanced `KanbanBoardContainer` to display pinned tasks in a dedicated `ObjectivesBoard`, improving task visibility.
- Modified `KanbanFilters` to support filtering by pinned tags, streamlining task management.
- Adjusted `TasksContext` to separate pinned tasks from regular tasks for better organization.

lib/types.ts

@@ -29,6 +29,7 @@ export interface Tag {
   id: string;
   name: string;
   color: string;
+  isPinned?: boolean; // Tag pour objectifs principaux
 }
 
 // Interface pour les logs de synchronisation