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/intercept/intercept.go

@@ -13,6 +13,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/ent/announcement"
 	"github.com/Wei-Shaw/sub2api/ent/announcementread"
 	"github.com/Wei-Shaw/sub2api/ent/apikey"
+	"github.com/Wei-Shaw/sub2api/ent/errorpassthroughrule"
 	"github.com/Wei-Shaw/sub2api/ent/group"
 	"github.com/Wei-Shaw/sub2api/ent/predicate"
 	"github.com/Wei-Shaw/sub2api/ent/promocode"
@@ -220,6 +221,33 @@ func (f TraverseAnnouncementRead) Traverse(ctx context.Context, q ent.Query) err
 	return fmt.Errorf("unexpected query type %T. expect *ent.AnnouncementReadQuery", q)
 }
 
+// The ErrorPassthroughRuleFunc type is an adapter to allow the use of ordinary function as a Querier.
+type ErrorPassthroughRuleFunc func(context.Context, *ent.ErrorPassthroughRuleQuery) (ent.Value, error)
+
+// Query calls f(ctx, q).
+func (f ErrorPassthroughRuleFunc) Query(ctx context.Context, q ent.Query) (ent.Value, error) {
+	if q, ok := q.(*ent.ErrorPassthroughRuleQuery); ok {
+		return f(ctx, q)
+	}
+	return nil, fmt.Errorf("unexpected query type %T. expect *ent.ErrorPassthroughRuleQuery", q)
+}
+
+// The TraverseErrorPassthroughRule type is an adapter to allow the use of ordinary function as Traverser.
+type TraverseErrorPassthroughRule func(context.Context, *ent.ErrorPassthroughRuleQuery) error
+
+// Intercept is a dummy implementation of Intercept that returns the next Querier in the pipeline.
+func (f TraverseErrorPassthroughRule) Intercept(next ent.Querier) ent.Querier {
+	return next
+}
+
+// Traverse calls f(ctx, q).
+func (f TraverseErrorPassthroughRule) Traverse(ctx context.Context, q ent.Query) error {
+	if q, ok := q.(*ent.ErrorPassthroughRuleQuery); ok {
+		return f(ctx, q)
+	}
+	return fmt.Errorf("unexpected query type %T. expect *ent.ErrorPassthroughRuleQuery", q)
+}
+
 // The GroupFunc type is an adapter to allow the use of ordinary function as a Querier.
 type GroupFunc func(context.Context, *ent.GroupQuery) (ent.Value, error)
 
@@ -584,6 +612,8 @@ func NewQuery(q ent.Query) (Query, error) {
 		return &query[*ent.AnnouncementQuery, predicate.Announcement, announcement.OrderOption]{typ: ent.TypeAnnouncement, tq: q}, nil
 	case *ent.AnnouncementReadQuery:
 		return &query[*ent.AnnouncementReadQuery, predicate.AnnouncementRead, announcementread.OrderOption]{typ: ent.TypeAnnouncementRead, tq: q}, nil
+	case *ent.ErrorPassthroughRuleQuery:
+		return &query[*ent.ErrorPassthroughRuleQuery, predicate.ErrorPassthroughRule, errorpassthroughrule.OrderOption]{typ: ent.TypeErrorPassthroughRule, tq: q}, nil
 	case *ent.GroupQuery:
 		return &query[*ent.GroupQuery, predicate.Group, group.OrderOption]{typ: ent.TypeGroup, tq: q}, nil
 	case *ent.PromoCodeQuery: