fix: 需要资格的商品每个订单消耗1个资格

- 移除后台商品管理的资格消耗设置
- 修改后端资格检查和扣除逻辑为每个订单项消耗1个资格
- 修改前端显示为需要1个资格

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/admin/Products.vue

@@ -133,17 +133,13 @@
         <div class="form-section">
           <div class="section-title">资格设置</div>
           <el-row :gutter="16">
-            <el-col :span="8">
+            <el-col :span="12">
               <el-form-item label="需要资格">
                 <el-switch v-model="form.require_credit" />
+                <span class="form-tip" v-if="form.require_credit" style="margin-left: 8px; color: rgba(255,255,255,0.5);">订单消耗1个资格</span>
               </el-form-item>
             </el-col>
-            <el-col :span="8">
-              <el-form-item label="资格消耗">
-                <el-input-number v-model="form.credit_cost" :min="0" style="width: 100%" :disabled="!form.require_credit" />
-              </el-form-item>
-            </el-col>
-            <el-col :span="8">
+            <el-col :span="12">
               <el-form-item label="资格奖励">
                 <el-input-number v-model="form.credit_reward" :min="0" style="width: 100%" />
               </el-form-item>

frontend/src/views/user/Cart.vue

@@ -67,7 +67,7 @@
                 <!-- 标签 -->
                 <div class="item-tags" v-if="item.product?.require_credit || item.product?.credit_reward > 0">
                   <el-tag v-if="item.product?.require_credit" size="small" type="warning">
-                    需要: {{ item.product?.credit_cost }}
+                    需要: 1 资格
                   </el-tag>
                   <el-tag v-if="item.product?.credit_reward > 0" size="small" type="success">
                     +{{ item.product?.credit_reward }}
@@ -430,7 +430,7 @@ function isOutOfStock(product: any): boolean {
 // 检查用户是否有足够资格购买
 function hasEnoughCredit(product: any): boolean {
   if (!product || !product.require_credit) return true
-  return userCredits.value >= (product.credit_cost || 0)
+  return userCredits.value >= 1
 }
 
 // 检查商品是否可以选择

frontend/src/views/user/ProductDetail.vue

@@ -34,7 +34,7 @@
           <p class="description">{{ product.description }}</p>
           <div class="meta">
             <el-tag v-if="product.require_credit" :type="hasEnoughCredit() ? 'warning' : 'danger'">
-              {{ $t('product.requireCredit') }}: {{ product.credit_cost * quantity }}
+              {{ $t('product.requireCredit') }}: 1
               <span v-if="!hasEnoughCredit()"> (资格不足)</span>
             </el-tag>
             <el-tag v-if="product.credit_reward > 0" type="success">+{{ product.credit_reward * quantity }} {{ $t('product.creditReward') }}</el-tag>
@@ -88,8 +88,7 @@ const productImages = computed(() => {
 // 检查用户是否有足够资格购买
 function hasEnoughCredit(): boolean {
   if (!product.value || !product.value.require_credit) return true
-  const totalCost = product.value.credit_cost * quantity.value
-  return userCredits.value >= totalCost
+  return userCredits.value >= 1
 }
 
 // 获取用户资格信息
@@ -114,8 +113,7 @@ onMounted(async () => {
 async function addToCart() {
   // 检查购物资格
   if (!hasEnoughCredit()) {
-    const totalCost = product.value.credit_cost * quantity.value
-    ElMessage.warning(`资格不足！需要 ${totalCost} 资格，您当前只有 ${userCredits.value} 资格`)
+    ElMessage.warning(`资格不足！该商品需要1个资格，您当前只有 ${userCredits.value} 资格`)
     return
   }