feat: 优惠管理合并重构与商品续费价格参数

- 合并优惠码/代金券为商品管理下优惠管理页面，卡片化展示与过期遮罩

- 用户组新增优惠绑定，商品关联改用懒加载树选择器

- 商品/套餐表单新增 renew_price、renew_recommend_rebate、renew_fixed_price

Co-authored-by: Cursor <cursoragent@cursor.com>

src/views/product/ProductGroup.vue

@@ -637,6 +637,20 @@
                   inactive-text="禁止"
                 />
               </el-form-item>
+              <el-form-item prop="renew_price" v-if="productForm.can_renew">
+                <template #label>
+                  <span>续费价格<span class="unit-suffix">（元，0 沿用商品价格）</span></span>
+                </template>
+                <el-input-number
+                  v-model="productForm.renew_price"
+                  :min="0"
+                  :precision="2"
+                  :step="0.01"
+                  placeholder="续费基础价格"
+                  controls-position="right"
+                  style="width: 100%"
+                />
+              </el-form-item>
               <el-form-item label="购买类型" prop="arg_type">
                 <el-select
                   v-model="productForm.arg_type"
@@ -723,6 +737,20 @@
                   style="width: 100%"
                 />
               </el-form-item>
+              <el-form-item prop="renew_recommend_rebate">
+                <template #label>
+                  <span>续费推介返还<span class="unit-suffix">（%，0 沿用推荐返还）</span></span>
+                </template>
+                <el-input-number
+                  v-model="productForm.renew_recommend_rebate"
+                  :min="0"
+                  :max="100"
+                  :disabled="!productForm.recommend"
+                  placeholder="续费推介返还百分比"
+                  controls-position="right"
+                  style="width: 100%"
+                />
+              </el-form-item>
               <el-form-item label="购买通知" prop="send_notice">
                 <el-switch
                   v-model="productForm.send_notice"
@@ -903,7 +931,9 @@ const productForm = reactive({
   require_real_name: false,
   sold_out: false,
   max_per_user: 0,
-  send_notice: false
+  send_notice: false,
+  renew_price: 0,
+  renew_recommend_rebate: 0
 })
 
 const productRules = {
@@ -1591,7 +1621,9 @@ const handleEditProduct = (product, parentGroupId) => {
     require_real_name: product.requireRealName ?? product.require_real_name ?? false,
     sold_out: !!product.soldOut,
     max_per_user: product.maxPerUser ?? product.max_per_user ?? 0,
-    send_notice: !!product.sendNotice
+    send_notice: !!product.sendNotice,
+    renew_price: (product.renewPrice ?? product.renew_price ?? 0) / 100,
+    renew_recommend_rebate: product.renewRecommendRebate ?? product.renew_recommend_rebate ?? 0
   })
   
   productDialogVisible.value = true
@@ -1620,7 +1652,9 @@ const submitProductForm = () => {
           require_real_name: productForm.require_real_name,
           sold_out: productForm.sold_out === true,
           max_per_user: Number(productForm.max_per_user) || 0,
-          send_notice: productForm.send_notice === true
+          send_notice: productForm.send_notice === true,
+          renew_price: Number(productForm.renew_price) || 0,
+          renew_recommend_rebate: Number(productForm.renew_recommend_rebate) || 0
         }
         
         let res