feat: Add TaskWarrior integration with TaskChampion

- Error handling with TaskError enum and TaskResult<T> alias
- Data models: Task, TaskPriority, TaskStatus, TaskAnnotation
- Advanced filtering: TaskFilter with hierarchical projects, tags
  (AND/OR), priority, due dates, and search
- TaskService: Full CRUD, tags, projects, annotations, dependencies,
  sync

src/main.rs

@@ -3,6 +3,7 @@ use crate::app::App;
 mod app;
 mod components;
 mod models;
+mod task;
 mod theme;
 mod view;