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/promocodeusage/promocodeusage.go

@@ -0,0 +1,125 @@
+// Code generated by ent, DO NOT EDIT.
+
+package promocodeusage
+
+import (
+	"time"
+
+	"entgo.io/ent/dialect/sql"
+	"entgo.io/ent/dialect/sql/sqlgraph"
+)
+
+const (
+	// Label holds the string label denoting the promocodeusage type in the database.
+	Label = "promo_code_usage"
+	// FieldID holds the string denoting the id field in the database.
+	FieldID = "id"
+	// FieldPromoCodeID holds the string denoting the promo_code_id field in the database.
+	FieldPromoCodeID = "promo_code_id"
+	// FieldUserID holds the string denoting the user_id field in the database.
+	FieldUserID = "user_id"
+	// FieldBonusAmount holds the string denoting the bonus_amount field in the database.
+	FieldBonusAmount = "bonus_amount"
+	// FieldUsedAt holds the string denoting the used_at field in the database.
+	FieldUsedAt = "used_at"
+	// EdgePromoCode holds the string denoting the promo_code edge name in mutations.
+	EdgePromoCode = "promo_code"
+	// EdgeUser holds the string denoting the user edge name in mutations.
+	EdgeUser = "user"
+	// Table holds the table name of the promocodeusage in the database.
+	Table = "promo_code_usages"
+	// PromoCodeTable is the table that holds the promo_code relation/edge.
+	PromoCodeTable = "promo_code_usages"
+	// PromoCodeInverseTable is the table name for the PromoCode entity.
+	// It exists in this package in order to avoid circular dependency with the "promocode" package.
+	PromoCodeInverseTable = "promo_codes"
+	// PromoCodeColumn is the table column denoting the promo_code relation/edge.
+	PromoCodeColumn = "promo_code_id"
+	// UserTable is the table that holds the user relation/edge.
+	UserTable = "promo_code_usages"
+	// UserInverseTable is the table name for the User entity.
+	// It exists in this package in order to avoid circular dependency with the "user" package.
+	UserInverseTable = "users"
+	// UserColumn is the table column denoting the user relation/edge.
+	UserColumn = "user_id"
+)
+
+// Columns holds all SQL columns for promocodeusage fields.
+var Columns = []string{
+	FieldID,
+	FieldPromoCodeID,
+	FieldUserID,
+	FieldBonusAmount,
+	FieldUsedAt,
+}
+
+// ValidColumn reports if the column name is valid (part of the table columns).
+func ValidColumn(column string) bool {
+	for i := range Columns {
+		if column == Columns[i] {
+			return true
+		}
+	}
+	return false
+}
+
+var (
+	// DefaultUsedAt holds the default value on creation for the "used_at" field.
+	DefaultUsedAt func() time.Time
+)
+
+// OrderOption defines the ordering options for the PromoCodeUsage queries.
+type OrderOption func(*sql.Selector)
+
+// ByID orders the results by the id field.
+func ByID(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldID, opts...).ToFunc()
+}
+
+// ByPromoCodeID orders the results by the promo_code_id field.
+func ByPromoCodeID(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldPromoCodeID, opts...).ToFunc()
+}
+
+// ByUserID orders the results by the user_id field.
+func ByUserID(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldUserID, opts...).ToFunc()
+}
+
+// ByBonusAmount orders the results by the bonus_amount field.
+func ByBonusAmount(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldBonusAmount, opts...).ToFunc()
+}
+
+// ByUsedAt orders the results by the used_at field.
+func ByUsedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldUsedAt, opts...).ToFunc()
+}
+
+// ByPromoCodeField orders the results by promo_code field.
+func ByPromoCodeField(field string, opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newPromoCodeStep(), sql.OrderByField(field, opts...))
+	}
+}
+
+// ByUserField orders the results by user field.
+func ByUserField(field string, opts ...sql.OrderTermOption) OrderOption {
+	return func(s *sql.Selector) {
+		sqlgraph.OrderByNeighborTerms(s, newUserStep(), sql.OrderByField(field, opts...))
+	}
+}
+func newPromoCodeStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(PromoCodeInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.M2O, true, PromoCodeTable, PromoCodeColumn),
+	)
+}
+func newUserStep() *sqlgraph.Step {
+	return sqlgraph.NewStep(
+		sqlgraph.From(Table, FieldID),
+		sqlgraph.To(UserInverseTable, FieldID),
+		sqlgraph.Edge(sqlgraph.M2O, true, UserTable, UserColumn),
+	)
+}