feat(07-01): add QuickAddItem migration, model, and query functions

- Create 003_quick_add_library.sql with quick_add_items table and user index
- Add QuickAddItem struct to models.go following Category pattern
- Add ListQuickAddItems, CreateQuickAddItem, UpdateQuickAddItem, DeleteQuickAddItem to queries.go

backend/internal/db/queries.go

@@ -525,6 +525,67 @@ func (q *Queries) ReorderTemplateItems(ctx context.Context, userID uuid.UUID, it
 	return tx.Commit(ctx)
 }
 
+// Quick Add Items
+
+func (q *Queries) ListQuickAddItems(ctx context.Context, userID uuid.UUID) ([]models.QuickAddItem, error) {
+	rows, err := q.pool.Query(ctx,
+		`SELECT id, user_id, name, icon, sort_order, created_at, updated_at
+		FROM quick_add_items WHERE user_id = $1 ORDER BY sort_order, name`, userID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("listing quick add items: %w", err)
+	}
+	defer rows.Close()
+
+	items := []models.QuickAddItem{}
+	for rows.Next() {
+		var i models.QuickAddItem
+		if err := rows.Scan(&i.ID, &i.UserID, &i.Name, &i.Icon, &i.SortOrder, &i.CreatedAt, &i.UpdatedAt); err != nil {
+			return nil, fmt.Errorf("scanning quick add item: %w", err)
+		}
+		items = append(items, i)
+	}
+	return items, nil
+}
+
+func (q *Queries) CreateQuickAddItem(ctx context.Context, userID uuid.UUID, name, icon string) (*models.QuickAddItem, error) {
+	i := &models.QuickAddItem{}
+	err := q.pool.QueryRow(ctx,
+		`INSERT INTO quick_add_items (user_id, name, icon, sort_order)
+		VALUES ($1, $2, $3, (SELECT COALESCE(MAX(sort_order), 0) + 1 FROM quick_add_items WHERE user_id = $1))
+		RETURNING id, user_id, name, icon, sort_order, created_at, updated_at`,
+		userID, name, icon,
+	).Scan(&i.ID, &i.UserID, &i.Name, &i.Icon, &i.SortOrder, &i.CreatedAt, &i.UpdatedAt)
+	if err != nil {
+		return nil, fmt.Errorf("creating quick add item: %w", err)
+	}
+	return i, nil
+}
+
+func (q *Queries) UpdateQuickAddItem(ctx context.Context, id, userID uuid.UUID, name, icon string, sortOrder int) (*models.QuickAddItem, error) {
+	i := &models.QuickAddItem{}
+	err := q.pool.QueryRow(ctx,
+		`UPDATE quick_add_items SET name = $3, icon = $4, sort_order = $5, updated_at = now()
+		WHERE id = $1 AND user_id = $2
+		RETURNING id, user_id, name, icon, sort_order, created_at, updated_at`,
+		id, userID, name, icon, sortOrder,
+	).Scan(&i.ID, &i.UserID, &i.Name, &i.Icon, &i.SortOrder, &i.CreatedAt, &i.UpdatedAt)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return nil, fmt.Errorf("quick add item not found")
+		}
+		return nil, fmt.Errorf("updating quick add item: %w", err)
+	}
+	return i, nil
+}
+
+func (q *Queries) DeleteQuickAddItem(ctx context.Context, id, userID uuid.UUID) error {
+	_, err := q.pool.Exec(ctx,
+		`DELETE FROM quick_add_items WHERE id = $1 AND user_id = $2`, id, userID,
+	)
+	return err
+}
+
 var monthNamesEN = map[time.Month]string{
 	time.January:   "January",
 	time.February:  "February",