Version: 0.9.66.dev.260504

后端：
1. 阶段 2 user/auth 服务边界落地，新增 `cmd/userauth` go-zero zrpc 服务、`services/userauth` 核心实现、gateway user API/zrpc client 与 shared contracts/ports，迁移注册、登录、刷新 token、登出、JWT、黑名单和 token 额度治理
2. gateway 与启动装配切流，`cmd/all` 只保留边缘路由、鉴权和轻量组合，通过 userauth zrpc 访问核心用户能力；拆分 MySQL/Redis 初始化与 AutoMigrate 边界，`userauth` 自迁 `users` 和 token 记账幂等表，`all` 不再迁用户表
3. 清退 Gin 单体旧 user/auth DAO、model、service、router、middleware 和 JWT handler，并同步调整 agent/schedule/cache/outbox 相关调用依赖
4. 补齐 refresh token 防并发重放、MySQL 幂等 token 记账、额度 `>=` 拦截和 RPC 错误映射，避免重复记账与内部错误透出

文档：
1. 新增《学习计划论坛与Token商店PRD》

backend/gateway/userauth/errors.go

@@ -0,0 +1,198 @@
+package userauth
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/LoveLosita/smartflow/backend/respond"
+	"google.golang.org/genproto/googleapis/rpc/errdetails"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// responseFromRPCError 负责把 user/auth 的 gRPC 错误反解回项目内的 respond.Response。
+//
+// 职责边界：
+// 1. 只在 gateway 边缘层使用，不下沉到服务实现里；
+// 2. 业务错误尽量恢复成 respond.Response，方便 API 层继续复用现有 DealWithError；
+// 3. 只要拿不到业务语义，就退化成普通 error，让上层按 500 处理。
+func responseFromRPCError(err error) error {
+	if err == nil {
+		return nil
+	}
+
+	st, ok := status.FromError(err)
+	if !ok {
+		return wrapRPCError(err)
+	}
+
+	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 = "userauth zrpc service internal error"
+		}
+		return wrapRPCError(errors.New(msg))
+	}
+
+	msg := strings.TrimSpace(st.Message())
+	if msg == "" {
+		msg = "userauth zrpc service rejected request"
+	}
+	return respond.Response{
+		Status: grpcCodeToRespondStatus(st.Code()),
+		Info:   msg,
+	}
+}
+
+func responseFromStatus(st *status.Status) (respond.Response, bool) {
+	if st == nil {
+		return respond.Response{}, false
+	}
+
+	if resp, ok := responseFromStatusDetails(st); ok {
+		return resp, true
+	}
+	if resp, ok := responseFromLegacyStatus(st.Code(), st.Message()); ok {
+		return resp, true
+	}
+	return respond.Response{}, false
+}
+
+func responseFromStatusDetails(st *status.Status) (respond.Response, bool) {
+	for _, detail := range st.Details() {
+		info, ok := detail.(*errdetails.ErrorInfo)
+		if !ok {
+			continue
+		}
+
+		statusValue := strings.TrimSpace(info.Reason)
+		if statusValue == "" {
+			statusValue = grpcCodeToRespondStatus(st.Code())
+		}
+		if statusValue == "" {
+			return respond.Response{}, false
+		}
+
+		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 responseFromLegacyStatus(code codes.Code, message string) (respond.Response, bool) {
+	trimmed := strings.TrimSpace(message)
+	if resp, ok := respondResponseByMessage(trimmed); ok {
+		return resp, true
+	}
+
+	switch code {
+	case codes.Unauthenticated:
+		if trimmed == "" {
+			trimmed = "unauthorized"
+		}
+		return respond.Response{Status: respond.ErrUnauthorized.Status, Info: trimmed}, true
+	case codes.AlreadyExists:
+		if trimmed == "" {
+			trimmed = "already exists"
+		}
+		return respond.Response{Status: respond.InvalidName.Status, Info: trimmed}, true
+	case codes.NotFound:
+		if trimmed == "" {
+			trimmed = "not found"
+		}
+		return respond.Response{Status: respond.WrongName.Status, Info: trimmed}, true
+	case codes.ResourceExhausted:
+		if trimmed == "" {
+			trimmed = respond.TokenUsageExceedsLimit.Info
+		}
+		return respond.Response{Status: respond.TokenUsageExceedsLimit.Status, Info: trimmed}, true
+	case codes.InvalidArgument:
+		if trimmed == "" {
+			trimmed = "invalid argument"
+		}
+		return respond.Response{Status: respond.MissingParam.Status, Info: trimmed}, true
+	case codes.Internal, codes.Unknown, codes.DataLoss:
+		if trimmed == "" {
+			trimmed = "userauth service internal error"
+		}
+		return respond.InternalError(errors.New(trimmed)), true
+	}
+
+	return respond.Response{}, false
+}
+
+func respondResponseByMessage(message string) (respond.Response, bool) {
+	switch strings.TrimSpace(message) {
+	case respond.MissingParam.Info:
+		return respond.MissingParam, true
+	case respond.WrongParamType.Info:
+		return respond.WrongParamType, true
+	case respond.ParamTooLong.Info:
+		return respond.ParamTooLong, true
+	case respond.InvalidName.Info:
+		return respond.InvalidName, true
+	case respond.WrongName.Info:
+		return respond.WrongName, true
+	case respond.WrongPwd.Info:
+		return respond.WrongPwd, true
+	case respond.WrongUsernameOrPwd.Info:
+		return respond.WrongUsernameOrPwd, true
+	case respond.MissingToken.Info:
+		return respond.MissingToken, true
+	case respond.InvalidTokenSingingMethod.Info:
+		return respond.InvalidTokenSingingMethod, true
+	case respond.InvalidToken.Info:
+		return respond.InvalidToken, true
+	case respond.InvalidClaims.Info:
+		return respond.InvalidClaims, true
+	case respond.ErrUnauthorized.Info:
+		return respond.ErrUnauthorized, true
+	case respond.InvalidRefreshToken.Info:
+		return respond.InvalidRefreshToken, true
+	case respond.WrongTokenType.Info:
+		return respond.WrongTokenType, true
+	case respond.UserLoggedOut.Info:
+		return respond.UserLoggedOut, true
+	case respond.WrongUserID.Info:
+		return respond.WrongUserID, true
+	case respond.TokenUsageExceedsLimit.Info:
+		return respond.TokenUsageExceedsLimit, true
+	}
+	return respond.Response{}, false
+}
+
+func grpcCodeToRespondStatus(code codes.Code) string {
+	switch code {
+	case codes.Unauthenticated:
+		return respond.ErrUnauthorized.Status
+	case codes.AlreadyExists:
+		return respond.InvalidName.Status
+	case codes.NotFound:
+		return respond.WrongName.Status
+	case codes.ResourceExhausted:
+		return respond.TokenUsageExceedsLimit.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 userauth zrpc 服务失败: %w", err)
+}