refactor: 重構 VendorProduct API 與新增進貨單重複檢查前端邏輯

1. 將 VendorProductController 中的 Eloquent 關聯操作改為透過 ProcurementService 使用 DB 操作，解除跨模組 Model 直接依賴。
2. ProcurementService 加入 vendor product 的資料存取方法。
3. 進貨單建立前端 (GoodsReceipt/Create.tsx) 新增重複進貨檢查與警告對話框邏輯。

app/Modules/Procurement/Contracts/ProcurementServiceInterface.php

@@ -79,4 +79,29 @@ interface ProcurementServiceInterface
      * @return Collection
      */
     public function getVendorsByIds(array $ids): Collection;
+
+    /**
+     * 新增供貨商品關聯
+     */
+    public function attachProductToVendor(int $vendorId, int $productId, ?float $lastPrice): void;
+
+    /**
+     * 更新供貨商品價格
+     */
+    public function updateVendorProductPrice(int $vendorId, int $productId, ?float $lastPrice): void;
+
+    /**
+     * 檢查廠商是否已有該供貨商品
+     */
+    public function checkVendorHasProduct(int $vendorId, int $productId): bool;
+
+    /**
+     * 取得供貨商品的價格
+     */
+    public function getVendorProductPrice(int $vendorId, int $productId): ?float;
+
+    /**
+     * 移除供貨商品關聯
+     */
+    public function detachProductFromVendor(int $vendorId, int $productId): void;
 }

app/Modules/Procurement/Controllers/VendorProductController.php

@@ -5,13 +5,15 @@ namespace App\Modules\Procurement\Controllers;
 use App\Http\Controllers\Controller;
 use App\Modules\Procurement\Models\Vendor;
 use App\Modules\Inventory\Contracts\InventoryServiceInterface;
+use App\Modules\Procurement\Contracts\ProcurementServiceInterface;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Log;
 
 class VendorProductController extends Controller
 {
     public function __construct(
-        protected InventoryServiceInterface $inventoryService
+        protected InventoryServiceInterface $inventoryService,
+        protected ProcurementServiceInterface $procurementService
     ) {}
 
     /**
@@ -25,13 +27,15 @@ class VendorProductController extends Controller
         ]);
 
         // 檢查是否已存在
-        if ($vendor->products()->where('product_id', $validated['product_id'])->exists()) {
+        if ($this->procurementService->checkVendorHasProduct($vendor->id, $validated['product_id'])) {
             return redirect()->back()->with('error', '該商品已在供貨清單中');
         }
 
-        $vendor->products()->attach($validated['product_id'], [
-            'last_price' => $validated['last_price'] ?? null
-        ]);
+        $this->procurementService->attachProductToVendor(
+            $vendor->id,
+            $validated['product_id'],
+            $validated['last_price'] ?? null
+        );
 
         // 記錄操作
         $product = $this->inventoryService->getProduct($validated['product_id']);
@@ -65,11 +69,13 @@ class VendorProductController extends Controller
         ]);
 
         // 獲取舊價格
-        $old_price = $vendor->products()->where('product_id', $productId)->first()?->pivot?->last_price;
+        $old_price = $this->procurementService->getVendorProductPrice($vendor->id, $productId);
 
-        $vendor->products()->updateExistingPivot($productId, [
-            'last_price' => $validated['last_price'] ?? null
-        ]);
+        $this->procurementService->updateVendorProductPrice(
+            $vendor->id,
+            $productId,
+            $validated['last_price'] ?? null
+        );
 
         // 記錄操作
         $product = $this->inventoryService->getProduct($productId);
@@ -102,9 +108,9 @@ class VendorProductController extends Controller
     {
         // 記錄操作 (需在 detach 前獲取資訊)
         $product = $this->inventoryService->getProduct($productId);
-        $old_price = $vendor->products()->where('product_id', $productId)->first()?->pivot?->last_price;
+        $old_price = $this->procurementService->getVendorProductPrice($vendor->id, $productId);
         
-        $vendor->products()->detach($productId);
+        $this->procurementService->detachProductFromVendor($vendor->id, $productId);
 
         if ($product) {
             activity()

app/Modules/Procurement/Services/ProcurementService.php

@@ -99,4 +99,52 @@ class ProcurementService implements ProcurementServiceInterface
     {
         return \App\Modules\Procurement\Models\Vendor::whereIn('id', $ids)->get(['id', 'name', 'code']);
     }
+
+    public function attachProductToVendor(int $vendorId, int $productId, ?float $lastPrice): void
+    {
+        \Illuminate\Support\Facades\DB::table('product_vendor')->insert([
+            'vendor_id' => $vendorId,
+            'product_id' => $productId,
+            'last_price' => $lastPrice,
+            'created_at' => now(),
+            'updated_at' => now(),
+        ]);
+    }
+
+    public function updateVendorProductPrice(int $vendorId, int $productId, ?float $lastPrice): void
+    {
+        \Illuminate\Support\Facades\DB::table('product_vendor')
+            ->where('vendor_id', $vendorId)
+            ->where('product_id', $productId)
+            ->update([
+                'last_price' => $lastPrice,
+                'updated_at' => now(),
+            ]);
+    }
+
+    public function checkVendorHasProduct(int $vendorId, int $productId): bool
+    {
+        return \Illuminate\Support\Facades\DB::table('product_vendor')
+            ->where('vendor_id', $vendorId)
+            ->where('product_id', $productId)
+            ->exists();
+    }
+
+    public function getVendorProductPrice(int $vendorId, int $productId): ?float
+    {
+        $pivot = \Illuminate\Support\Facades\DB::table('product_vendor')
+            ->where('vendor_id', $vendorId)
+            ->where('product_id', $productId)
+            ->first();
+
+        return $pivot ? (float) $pivot->last_price : null;
+    }
+
+    public function detachProductFromVendor(int $vendorId, int $productId): void
+    {
+        \Illuminate\Support\Facades\DB::table('product_vendor')
+            ->where('vendor_id', $vendorId)
+            ->where('product_id', $productId)
+            ->delete();
+    }
 }