feat: 新增全局错误透传规则功能

支持管理员配置上游错误如何返回给客户端：
- 新增 ErrorPassthroughRule 数据模型和 Ent Schema
- 实现规则的 CRUD API（/admin/error-passthrough-rules）
- 支持按错误码、关键词匹配，支持 any/all 匹配模式
- 支持按平台过滤（anthropic/openai/gemini/antigravity）
- 支持透传或自定义响应状态码和错误消息
- 实现两级缓存（Redis + 本地内存）和多实例同步
- 集成到 gateway_handler 的错误处理流程
- 新增前端管理界面组件
- 新增单元测试覆盖核心匹配逻辑

优化：
- 移除 refreshLocalCache 中的冗余排序（数据库已排序）
- 后端 Validate() 增加匹配条件非空校验

backend/ent/errorpassthroughrule/errorpassthroughrule.go

@@ -0,0 +1,161 @@
+// Code generated by ent, DO NOT EDIT.
+
+package errorpassthroughrule
+
+import (
+	"time"
+
+	"entgo.io/ent/dialect/sql"
+)
+
+const (
+	// Label holds the string label denoting the errorpassthroughrule type in the database.
+	Label = "error_passthrough_rule"
+	// FieldID holds the string denoting the id field in the database.
+	FieldID = "id"
+	// FieldCreatedAt holds the string denoting the created_at field in the database.
+	FieldCreatedAt = "created_at"
+	// FieldUpdatedAt holds the string denoting the updated_at field in the database.
+	FieldUpdatedAt = "updated_at"
+	// FieldName holds the string denoting the name field in the database.
+	FieldName = "name"
+	// FieldEnabled holds the string denoting the enabled field in the database.
+	FieldEnabled = "enabled"
+	// FieldPriority holds the string denoting the priority field in the database.
+	FieldPriority = "priority"
+	// FieldErrorCodes holds the string denoting the error_codes field in the database.
+	FieldErrorCodes = "error_codes"
+	// FieldKeywords holds the string denoting the keywords field in the database.
+	FieldKeywords = "keywords"
+	// FieldMatchMode holds the string denoting the match_mode field in the database.
+	FieldMatchMode = "match_mode"
+	// FieldPlatforms holds the string denoting the platforms field in the database.
+	FieldPlatforms = "platforms"
+	// FieldPassthroughCode holds the string denoting the passthrough_code field in the database.
+	FieldPassthroughCode = "passthrough_code"
+	// FieldResponseCode holds the string denoting the response_code field in the database.
+	FieldResponseCode = "response_code"
+	// FieldPassthroughBody holds the string denoting the passthrough_body field in the database.
+	FieldPassthroughBody = "passthrough_body"
+	// FieldCustomMessage holds the string denoting the custom_message field in the database.
+	FieldCustomMessage = "custom_message"
+	// FieldDescription holds the string denoting the description field in the database.
+	FieldDescription = "description"
+	// Table holds the table name of the errorpassthroughrule in the database.
+	Table = "error_passthrough_rules"
+)
+
+// Columns holds all SQL columns for errorpassthroughrule fields.
+var Columns = []string{
+	FieldID,
+	FieldCreatedAt,
+	FieldUpdatedAt,
+	FieldName,
+	FieldEnabled,
+	FieldPriority,
+	FieldErrorCodes,
+	FieldKeywords,
+	FieldMatchMode,
+	FieldPlatforms,
+	FieldPassthroughCode,
+	FieldResponseCode,
+	FieldPassthroughBody,
+	FieldCustomMessage,
+	FieldDescription,
+}
+
+// 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 (
+	// DefaultCreatedAt holds the default value on creation for the "created_at" field.
+	DefaultCreatedAt func() time.Time
+	// DefaultUpdatedAt holds the default value on creation for the "updated_at" field.
+	DefaultUpdatedAt func() time.Time
+	// UpdateDefaultUpdatedAt holds the default value on update for the "updated_at" field.
+	UpdateDefaultUpdatedAt func() time.Time
+	// NameValidator is a validator for the "name" field. It is called by the builders before save.
+	NameValidator func(string) error
+	// DefaultEnabled holds the default value on creation for the "enabled" field.
+	DefaultEnabled bool
+	// DefaultPriority holds the default value on creation for the "priority" field.
+	DefaultPriority int
+	// DefaultMatchMode holds the default value on creation for the "match_mode" field.
+	DefaultMatchMode string
+	// MatchModeValidator is a validator for the "match_mode" field. It is called by the builders before save.
+	MatchModeValidator func(string) error
+	// DefaultPassthroughCode holds the default value on creation for the "passthrough_code" field.
+	DefaultPassthroughCode bool
+	// DefaultPassthroughBody holds the default value on creation for the "passthrough_body" field.
+	DefaultPassthroughBody bool
+)
+
+// OrderOption defines the ordering options for the ErrorPassthroughRule 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()
+}
+
+// ByCreatedAt orders the results by the created_at field.
+func ByCreatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldCreatedAt, opts...).ToFunc()
+}
+
+// ByUpdatedAt orders the results by the updated_at field.
+func ByUpdatedAt(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldUpdatedAt, opts...).ToFunc()
+}
+
+// ByName orders the results by the name field.
+func ByName(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldName, opts...).ToFunc()
+}
+
+// ByEnabled orders the results by the enabled field.
+func ByEnabled(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldEnabled, opts...).ToFunc()
+}
+
+// ByPriority orders the results by the priority field.
+func ByPriority(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldPriority, opts...).ToFunc()
+}
+
+// ByMatchMode orders the results by the match_mode field.
+func ByMatchMode(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldMatchMode, opts...).ToFunc()
+}
+
+// ByPassthroughCode orders the results by the passthrough_code field.
+func ByPassthroughCode(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldPassthroughCode, opts...).ToFunc()
+}
+
+// ByResponseCode orders the results by the response_code field.
+func ByResponseCode(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldResponseCode, opts...).ToFunc()
+}
+
+// ByPassthroughBody orders the results by the passthrough_body field.
+func ByPassthroughBody(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldPassthroughBody, opts...).ToFunc()
+}
+
+// ByCustomMessage orders the results by the custom_message field.
+func ByCustomMessage(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldCustomMessage, opts...).ToFunc()
+}
+
+// ByDescription orders the results by the description field.
+func ByDescription(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldDescription, opts...).ToFunc()
+}