Version: 0.9.69.dev.260504

后端：
1. 阶段 4 active-scheduler 服务边界落地，新增 `cmd/active-scheduler`、`services/active_scheduler`、`shared/contracts/activescheduler` 和 active-scheduler port，迁移 dry-run、trigger、preview、confirm zrpc 能力
2. active-scheduler outbox consumer、relay、retry loop 和 due job scanner 迁入独立服务入口，gateway `/active-schedule/*` 改为通过 zrpc client 调用
3. gateway 目录收口为 `gateway/api` + `gateway/client`，统一归档 userauth、notification、active-scheduler 的 HTTP 门面和 zrpc client
4. 将旧 `backend/active_scheduler` 领域核心下沉到 `services/active_scheduler/core`，清退旧根目录活跃实现，并补充 active-scheduler 启动期跨域依赖表检查
5. 调整单体启动与 outbox 归属，`cmd/all` 不再启动 active-scheduler workflow、scanner 或 handler

文档：
1. 更新微服务迁移计划，将阶段 4 active-scheduler 标记为首轮收口完成，并明确下一阶段进入 schedule / task / course / task-class

backend/gateway/client/activescheduler/errors.go

@@ -0,0 +1,116 @@
+package activescheduler
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/LoveLosita/smartflow/backend/respond"
+	contracts "github.com/LoveLosita/smartflow/backend/shared/contracts/activescheduler"
+	"google.golang.org/genproto/googleapis/rpc/errdetails"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+const activeSchedulerApplyErrorDomain = "smartflow.active_scheduler.apply"
+
+// responseFromRPCError 负责把 active-scheduler 的 gRPC 错误反解回项目内错误。
+//
+// 职责边界：
+// 1. confirm/apply 业务错误恢复为 shared/contracts/activescheduler.ApplyError；
+// 2. 普通业务错误恢复为 respond.Response，供 API 层复用 DealWithError；
+// 3. 服务不可用或未知内部错误包装成普通 error，避免误报成用户可修正的参数问题。
+func responseFromRPCError(err error) error {
+	if err == nil {
+		return nil
+	}
+
+	st, ok := status.FromError(err)
+	if !ok {
+		return wrapRPCError(err)
+	}
+	if applyErr, ok := applyErrorFromStatus(st); ok {
+		return applyErr
+	}
+	if resp, ok := responseFromStatus(st); ok {
+		return resp
+	}
+
+	switch st.Code() {
+	case codes.Internal, codes.Unknown, codes.Unavailable, codes.DeadlineExceeded, codes.DataLoss, codes.Unimplemented:
+		msg := strings.TrimSpace(st.Message())
+		if msg == "" {
+			msg = "active-scheduler zrpc service internal error"
+		}
+		return wrapRPCError(errors.New(msg))
+	}
+
+	msg := strings.TrimSpace(st.Message())
+	if msg == "" {
+		msg = "active-scheduler zrpc service rejected request"
+	}
+	return respond.Response{Status: grpcCodeToRespondStatus(st.Code()), Info: msg}
+}
+
+func applyErrorFromStatus(st *status.Status) (*contracts.ApplyError, bool) {
+	for _, detail := range st.Details() {
+		info, ok := detail.(*errdetails.ErrorInfo)
+		if !ok || info.Domain != activeSchedulerApplyErrorDomain {
+			continue
+		}
+		message := strings.TrimSpace(st.Message())
+		if message == "" && info.Metadata != nil {
+			message = strings.TrimSpace(info.Metadata["info"])
+		}
+		return &contracts.ApplyError{
+			Code:    contracts.ApplyErrorCode(strings.TrimSpace(info.Reason)),
+			Message: message,
+		}, true
+	}
+	return nil, false
+}
+
+func responseFromStatus(st *status.Status) (respond.Response, bool) {
+	if st == nil {
+		return respond.Response{}, false
+	}
+	for _, detail := range st.Details() {
+		info, ok := detail.(*errdetails.ErrorInfo)
+		if !ok {
+			continue
+		}
+		statusValue := strings.TrimSpace(info.Reason)
+		if statusValue == "" {
+			statusValue = grpcCodeToRespondStatus(st.Code())
+		}
+		message := strings.TrimSpace(st.Message())
+		if message == "" && info.Metadata != nil {
+			message = strings.TrimSpace(info.Metadata["info"])
+		}
+		if message == "" {
+			message = statusValue
+		}
+		return respond.Response{Status: statusValue, Info: message}, true
+	}
+	return respond.Response{}, false
+}
+
+func grpcCodeToRespondStatus(code codes.Code) string {
+	switch code {
+	case codes.Unauthenticated:
+		return respond.ErrUnauthorized.Status
+	case codes.InvalidArgument:
+		return respond.MissingParam.Status
+	case codes.Internal, codes.Unknown, codes.DataLoss:
+		return "500"
+	default:
+		return "400"
+	}
+}
+
+func wrapRPCError(err error) error {
+	if err == nil {
+		return nil
+	}
+	return fmt.Errorf("调用 active-scheduler zrpc 服务失败: %w", err)
+}