feat: 实现注册优惠码功能

- 支持创建/编辑/删除优惠码，设置赠送金额和使用限制
  - 注册页面实时验证优惠码并显示赠送金额
  - 支持 URL 参数自动填充 (?promo=CODE)
  - 添加优惠码验证接口速率限制
  - 使用数据库行锁防止并发超限
  - 新增后台优惠码管理页面，支持复制注册链接

backend/ent/user/user.go

@@ -51,6 +51,8 @@ const (
 	EdgeUsageLogs = "usage_logs"
 	// EdgeAttributeValues holds the string denoting the attribute_values edge name in mutations.
 	EdgeAttributeValues = "attribute_values"
+	// EdgePromoCodeUsages holds the string denoting the promo_code_usages edge name in mutations.
+	EdgePromoCodeUsages = "promo_code_usages"
 	// EdgeUserAllowedGroups holds the string denoting the user_allowed_groups edge name in mutations.
 	EdgeUserAllowedGroups = "user_allowed_groups"
 	// Table holds the table name of the user in the database.
@@ -102,6 +104,13 @@ const (
 	AttributeValuesInverseTable = "user_attribute_values"
 	// AttributeValuesColumn is the table column denoting the attribute_values relation/edge.
 	AttributeValuesColumn = "user_id"
+	// PromoCodeUsagesTable is the table that holds the promo_code_usages relation/edge.
+	PromoCodeUsagesTable = "promo_code_usages"
+	// PromoCodeUsagesInverseTable is the table name for the PromoCodeUsage entity.
+	// It exists in this package in order to avoid circular dependency with the "promocodeusage" package.
+	PromoCodeUsagesInverseTable = "promo_code_usages"
+	// PromoCodeUsagesColumn is the table column denoting the promo_code_usages relation/edge.
+	PromoCodeUsagesColumn = "user_id"
 	// UserAllowedGroupsTable is the table that holds the user_allowed_groups relation/edge.
 	UserAllowedGroupsTable = "user_allowed_groups"
 	// UserAllowedGroupsInverseTable is the table name for the UserAllowedGroup entity.
@@ -342,6 +351,20 @@ func ByAttributeValues(term sql.OrderTerm, terms ...sql.OrderTerm) OrderOption {
 	}
 }
 
+// ByPromoCodeUsagesCount orders the results by promo_code_usages count.
+func ByPromoCodeUsagesCount(opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborsCount(s, newPromoCodeUsagesStep(), opts...)
+	}
+}
+
+// ByPromoCodeUsages orders the results by promo_code_usages terms.
+func ByPromoCodeUsages(term sql.OrderTerm, terms ...sql.OrderTerm) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newPromoCodeUsagesStep(), append([]sql.OrderTerm{term}, terms...)...)
+	}
+}
+
 // ByUserAllowedGroupsCount orders the results by user_allowed_groups count.
 func ByUserAllowedGroupsCount(opts ...sql.OrderTermOption) OrderOption {
 	return func(s *sql.Selector) {
@@ -404,6 +427,13 @@ func newAttributeValuesStep() *sqlgraph.Step {
 		sqlgraph.Edge(sqlgraph.O2M, false, AttributeValuesTable, AttributeValuesColumn),
 	)
 }
+func newPromoCodeUsagesStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(PromoCodeUsagesInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.O2M, false, PromoCodeUsagesTable, PromoCodeUsagesColumn),
+	)
+}
 func newUserAllowedGroupsStep() *sqlgraph.Step {
 	return sqlgraph.NewStep(
 		sqlgraph.From(Table, FieldID),

backend/ent/user/where.go

@@ -871,6 +871,29 @@ func HasAttributeValuesWith(preds ...predicate.UserAttributeValue) predicate.Use
 	})
 }
 
+// HasPromoCodeUsages applies the HasEdge predicate on the "promo_code_usages" edge.
+func HasPromoCodeUsages() predicate.User {
+	return predicate.User(func(s *sql.Selector) {
+		step := sqlgraph.NewStep(
+			sqlgraph.From(Table, FieldID),
+			sqlgraph.Edge(sqlgraph.O2M, false, PromoCodeUsagesTable, PromoCodeUsagesColumn),
+		)
+		sqlgraph.HasNeighbors(s, step)
+	})
+}
+
+// HasPromoCodeUsagesWith applies the HasEdge predicate on the "promo_code_usages" edge with a given conditions (other predicates).
+func HasPromoCodeUsagesWith(preds ...predicate.PromoCodeUsage) predicate.User {
+	return predicate.User(func(s *sql.Selector) {
+		step := newPromoCodeUsagesStep()
+		sqlgraph.HasNeighborsWith(s, step, func(s *sql.Selector) {
+			for _, p := range preds {
+				p(s)
+			}
+		})
+	})
+}
+
 // HasUserAllowedGroups applies the HasEdge predicate on the "user_allowed_groups" edge.
 func HasUserAllowedGroups() predicate.User {
 	return predicate.User(func(s *sql.Selector) {