feat(barcode): admin barcode CRUD endpoints + UI; show extra barcodes publicly

Wire the multi-barcode store layer to HTTP and the operator console:

- adminhandler: add POST /products/{id}/barcodes, DELETE
  /products/{id}/barcodes/{barcodeID}, and POST .../primary. A barcode
  owned by another product returns 409 with the conflicting product
  (gtin/product_id/product_name); an invalid GTIN returns 400.
- admin-frontend: BarcodesCard on the product detail page lists all
  barcodes (primary starred), adds with type/pack-level/region, sets
  primary, and deletes; audit labels for the new actions.
- public-frontend: product detail surfaces non-primary barcodes so a
  case/region code resolves and is visible to consumers.

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

public-frontend/src/components/ProductView.tsx

@@ -60,6 +60,29 @@ export default function ProductView({ id, onBack }: { id: string; onBack: () =>
         <div className="mt-4">
           <Row label="品牌" value={p.brand} />
           <Row label="条码 (GTIN)" value={p.gtin} />
+          {(() => {
+            const others = (p.barcodes || []).filter(
+              (b) => !b.is_primary && b.gtin !== p.gtin,
+            );
+            return others.length ? (
+              <Row
+                label="其他条码"
+                value={
+                  <div className="flex flex-wrap gap-1.5">
+                    {others.map((b) => (
+                      <span
+                        key={b.gtin}
+                        className="font-mono text-xs bg-gray-100 text-gray-600 rounded px-1.5 py-0.5"
+                        title={`${b.gtin_type} · ${b.pack_level}`}
+                      >
+                        {b.gtin}
+                      </span>
+                    ))}
+                  </div>
+                }
+              />
+            ) : null;
+          })()}
           <Row label="品类" value={p.category_path} />
           <Row
             label="净含量"

public-frontend/src/types.ts

@@ -6,9 +6,18 @@ export interface ProductSummary {
   category_path: string | null;
 }
 
+export interface Barcode {
+  gtin: string;
+  gtin_type: string;
+  pack_level: string;
+  region: string | null;
+  is_primary: boolean;
+}
+
 export interface Product {
   id: string;
   gtin: string | null;
+  barcodes?: Barcode[] | null;
   name: string;
   brand: string | null;
   category_path: string | null;