refactor(idgen): centralize negative ID handling via panic

Restore NextUint64ID() to uint64-only API so callers need no error
checks. Retry logic stays in idgen; after 3 negative values it panics
instead of returning 0, preventing silent NULL primary keys.

internal/model/errs.go

@@ -5,7 +5,6 @@ package model
 
 const (
 	errRegistrationDisabled                 = "注册已关闭"
-	errInvalidUserID                        = "用户 ID 生成失败"
 	errDatabaseNotInitialized               = "database not initialized"
 	errUsernameExists                       = "用户名已存在"
 	errEmailAlreadyBound                    = "该邮箱已被其他账号绑定"

internal/model/task_execution.go

@@ -60,11 +60,7 @@ func (TaskExecution) TableName() string {
 
 // CreateTaskExecution 创建任务执行记录
 func CreateTaskExecution(ctx context.Context, execution *TaskExecution) error {
-	id, err := idgen.NextUint64ID()
-	if err != nil {
-		return err
-	}
-	execution.ID = id
+	execution.ID = idgen.NextUint64ID()
 	return db.DB(ctx).Create(execution).Error
 }
 

internal/model/users.go

@@ -134,11 +134,7 @@ func (u *User) assignIDIfMissing() error {
 	if u.ID != 0 {
 		return nil
 	}
-	id, err := idgen.NextUint64ID()
-	if err != nil {
-		return errors.New(errInvalidUserID)
-	}
-	u.ID = id
+	u.ID = idgen.NextUint64ID()
 	return nil
 }