feat: [商品管理] 優化商品匯入邏輯，支援 13 碼條碼自動生成、Upsert 更新機制與 Excel 說明工作表

app/Modules/Inventory/Controllers/ProductController.php

@@ -197,6 +197,10 @@ class ProductController extends Controller
             $validated['code'] = $this->generateRandomCode();
         }
 
+        if (empty($validated['barcode'])) {
+            $validated['barcode'] = $this->generateRandomBarcode();
+        }
+
         $product = Product::create($validated);
 
         return redirect()->route('products.index')->with('success', '商品已建立');
@@ -260,6 +264,10 @@ class ProductController extends Controller
             $validated['code'] = $this->generateRandomCode();
         }
 
+        if (empty($validated['barcode'])) {
+            $validated['barcode'] = $this->generateRandomBarcode();
+        }
+
         $product->update($validated);
 
         if ($request->input('from') === 'show') {
@@ -328,4 +336,21 @@ class ProductController extends Controller
 
         return $code;
     }
+
+    /**
+     * 生成隨機 13 碼條碼 (純數字)
+     */
+    private function generateRandomBarcode(): string
+    {
+        $barcode = '';
+        
+        do {
+            $barcode = '';
+            for ($i = 0; $i < 13; $i++) {
+                $barcode .= rand(0, 9);
+            }
+        } while (Product::where('barcode', $barcode)->exists());
+
+        return $barcode;
+    }
 }