feat(admin): sortable product list column headers

Click a column header (名称/品牌/条码/品类/状态/质量分) to sort asc, click
again for desc, and a third time to clear back to the default
most-recently-updated order. Sort key/direction are whitelisted server-side.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

api/internal/adminstore/adminstore.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"errors"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/jackc/pgx/v5"
@@ -50,8 +51,34 @@ type ProductRow struct {
 	UpdatedAt    string   `json:"updated_at"`
 }
 
+// productSortColumns whitelists the sortable list columns, mapping the API sort
+// key to a SQL expression. NULLs sort last regardless of direction.
+var productSortColumns = map[string]string{
+	"name":          "p.name",
+	"brand":         "b.name",
+	"gtin":          "p.gtin",
+	"category_path": "c.path",
+	"status":        "p.status",
+	"quality_score": "p.quality_score",
+	"updated_at":    "p.updated_at",
+}
+
+// productOrderBy returns a safe ORDER BY clause for the given sort key/direction,
+// falling back to the default (most recently updated first) for unknown keys.
+func productOrderBy(sort, order string) string {
+	col, ok := productSortColumns[sort]
+	if !ok {
+		return "p.updated_at DESC"
+	}
+	dir := "ASC"
+	if strings.EqualFold(order, "desc") {
+		dir = "DESC"
+	}
+	return col + " " + dir + " NULLS LAST, p.updated_at DESC"
+}
+
 // ListProducts returns a paginated, optionally name/gtin-filtered list.
-func (s *Store) ListProducts(ctx context.Context, q string, limit, offset int) ([]ProductRow, int, error) {
+func (s *Store) ListProducts(ctx context.Context, q, sort, order string, limit, offset int) ([]ProductRow, int, error) {
 	args := []any{}
 	where := "WHERE 1=1"
 	if q != "" {
@@ -84,7 +111,8 @@ FROM product p
 LEFT JOIN brand b ON b.id = p.brand_id
 LEFT JOIN category c ON c.id = p.category_id
 LEFT JOIN food_detail f ON f.product_id = p.id ` + where +
-		" ORDER BY p.updated_at DESC LIMIT $" + strconv.Itoa(len(args)-1) + " OFFSET $" + strconv.Itoa(len(args))
+		" ORDER BY " + productOrderBy(sort, order) +
+		" LIMIT $" + strconv.Itoa(len(args)-1) + " OFFSET $" + strconv.Itoa(len(args))
 
 	rows, err := s.pool.Query(ctx, sql, args...)
 	if err != nil {