feat: task trash, triage trash and retention settings for every area; admin can forbid keeping things for good

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

internal/storage/thoughts.go

@@ -523,6 +523,8 @@ func (s *Store) UpdateThoughtDetails(userID, thoughtID string, content *string,
 	return thought, nil
 }
 
+// DeleteThought: a task goes to the task trash (task_trash.go); anything else (a thought from the inbox
+// or the triage trash) is deleted for good.
 func (s *Store) DeleteThought(userID, thoughtID string) error {
 	thought, err := s.GetThoughtByID(userID, thoughtID)
 	if err != nil {
@@ -531,6 +533,10 @@ func (s *Store) DeleteThought(userID, thoughtID string) error {
 	if err := s.ensureTaskListWritable(userID, thought.TaskListID); err != nil {
 		return err
 	}
+	// Tasks as in completedTaskSQL: kept, or converted into a task
+	if thought.Status == domain.StatusKept || (thought.Status == domain.StatusConverted && thought.ConvertedType == "task") {
+		return s.trashTask(thought.ID, userID)
+	}
 	_, err = s.db.Exec(`DELETE FROM thoughts WHERE id = ?`, thought.ID)
 	return err
 }