feat: select text across bullets and delete it like a text editor; Ctrl+Z in tasks; notes and lists without emoji; custom done columns complete tasks

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

internal/storage/documents.go

@@ -958,3 +958,15 @@ func (s *Store) GetCollaborators(currentUserID string) ([]domain.User, error) {
 	}
 	return users, nil
 }
+
+// ClearIcon removes the icon of a note, task list or list (created on purpose without one; the create
+// functions put in a default for an empty icon).
+func (s *Store) ClearIcon(table, id string) error {
+	switch table {
+	case "documents", "task_lists", "lists":
+	default:
+		return fmt.Errorf("unknown table %q", table)
+	}
+	_, err := s.db.Exec(`UPDATE `+table+` SET icon = '' WHERE id = ?`, id)
+	return err
+}