fix(billing): allow clearing group quota limits and treat 0 as zero-limit

Previously, v-model.number produced "" when input was cleared, causing
JSON decode errors on the backend. Also, normalizeLimit treated 0 as
"unlimited" which prevented setting a zero quota. Now "" is converted
to null (unlimited) in frontend, and 0 is preserved as a valid limit.

Closes Wei-Shaw/sub2api#1021

backend/internal/service/admin_service.go

@@ -832,7 +832,7 @@ func (s *adminServiceImpl) CreateGroup(ctx context.Context, input *CreateGroupIn
 		subscriptionType = SubscriptionTypeStandard
 	}
 
-	// 限额字段：0 和 nil 都表示"无限制"
+	// 限额字段：nil/负数 表示"无限制"，0 表示"不允许用量"，正数表示具体限额
 	dailyLimit := normalizeLimit(input.DailyLimitUSD)
 	weeklyLimit := normalizeLimit(input.WeeklyLimitUSD)
 	monthlyLimit := normalizeLimit(input.MonthlyLimitUSD)
@@ -944,9 +944,9 @@ func (s *adminServiceImpl) CreateGroup(ctx context.Context, input *CreateGroupIn
 	return group, nil
 }
 
-// normalizeLimit 将 0 或负数转换为 nil（表示无限制）
+// normalizeLimit 将负数转换为 nil（表示无限制），0 保留（表示限额为零）
 func normalizeLimit(limit *float64) *float64 {
-	if limit == nil || *limit <= 0 {
+	if limit == nil || *limit < 0 {
 		return nil
 	}
 	return limit
@@ -1058,16 +1058,11 @@ func (s *adminServiceImpl) UpdateGroup(ctx context.Context, id int64, input *Upd
 	if input.SubscriptionType != "" {
 		group.SubscriptionType = input.SubscriptionType
 	}
-	// 限额字段：0 和 nil 都表示"无限制"，正数表示具体限额
-	if input.DailyLimitUSD != nil {
+	// 限额字段：nil/负数 表示"无限制"，0 表示"不允许用量"，正数表示具体限额
+	// 前端始终发送这三个字段，无需 nil 守卫
 	group.DailyLimitUSD = normalizeLimit(input.DailyLimitUSD)
-	}
-	if input.WeeklyLimitUSD != nil {
 	group.WeeklyLimitUSD = normalizeLimit(input.WeeklyLimitUSD)
-	}
-	if input.MonthlyLimitUSD != nil {
 	group.MonthlyLimitUSD = normalizeLimit(input.MonthlyLimitUSD)
-	}
 	// 图片生成计费配置：负数表示清除（使用默认价格）
 	if input.ImagePrice1K != nil {
 		group.ImagePrice1K = normalizePrice(input.ImagePrice1K)

frontend/src/views/admin/GroupsView.vue

@@ -2382,6 +2382,11 @@ const handleCreateGroup = async () => {
       sora_storage_quota_bytes: createQuotaGb ? Math.round(createQuotaGb * 1024 * 1024 * 1024) : 0,
       model_routing: convertRoutingRulesToApiFormat(createModelRoutingRules.value)
     }
+    // v-model.number 清空输入框时产生 ""，转为 null 让后端设为无限制
+    const emptyToNull = (v: any) => v === '' ? null : v
+    requestData.daily_limit_usd = emptyToNull(requestData.daily_limit_usd)
+    requestData.weekly_limit_usd = emptyToNull(requestData.weekly_limit_usd)
+    requestData.monthly_limit_usd = emptyToNull(requestData.monthly_limit_usd)
     await adminAPI.groups.create(requestData)
     appStore.showSuccess(t('admin.groups.groupCreated'))
     closeCreateModal()
@@ -2465,6 +2470,11 @@ const handleUpdateGroup = async () => {
           : editForm.fallback_group_id_on_invalid_request,
       model_routing: convertRoutingRulesToApiFormat(editModelRoutingRules.value)
     }
+    // v-model.number 清空输入框时产生 ""，转为 null 让后端设为无限制
+    const emptyToNull = (v: any) => v === '' ? null : v
+    payload.daily_limit_usd = emptyToNull(payload.daily_limit_usd)
+    payload.weekly_limit_usd = emptyToNull(payload.weekly_limit_usd)
+    payload.monthly_limit_usd = emptyToNull(payload.monthly_limit_usd)
     await adminAPI.groups.update(editingGroup.value.id, payload)
     appStore.showSuccess(t('admin.groups.groupUpdated'))
     closeEditModal()