feat: complete tag management and UI integration

- Marked multiple tasks as completed in TODO.md related to tag management features.
- Replaced manual tag input with `TagInput` component in `CreateTaskForm`, `EditTaskForm`, and `QuickAddTask` for better UX.
- Updated `TaskCard` to display tags using `TagDisplay` with color support.
- Enhanced `TasksService` to manage task-tag relationships with CRUD operations.
- Integrated tag management into the global context for better accessibility across components.

prisma/schema.prisma

@@ -18,7 +18,6 @@ model Task {
   priority    String   @default("medium")
   source      String   // "reminders" | "jira"
   sourceId    String?  // ID dans le système source
-  tagsJson    String   @default("[]") // JSON string des tags pour compatibilité
   dueDate     DateTime?
   completedAt DateTime?
   createdAt   DateTime @default(now())