在 plugin-auth 中添加 SysUserPreference 系统对象，支持用户偏好存储

[xuyushun441-sys]

背景

框架当前缺少用户偏好（theme、locale、timezone、sidebar 状态等）的持久化能力。Config Resolution 文档（content/docs/protocol/objectos/config-resolution.mdx）已定义了 User Preferences 作为配置分层体系的第 2 层（Runtime > User Preferences > Tenant > Env），但代码层面尚未落地对应的 object schema。

方案

直接将 user_preference 作为系统对象放入 plugin-auth——与 SysUser、SysSession 等同属 identity 领域，遵循已有的 sys namespace 规范。
export const SysUserPreference = ObjectSchema.create({
namespace: 'sys',
name: 'user_preference',
label: 'User Preference',
pluralLabel: 'User Preferences',
icon: 'settings',
isSystem: true,
description: 'Per-user key-value preferences (theme, locale, etc.)',
titleFormat: '{key}',
compactLayout: ['user_id', 'key'],

fields: {
id: Field.text({
label: 'Preference ID',
required: true,
readonly: true,
}),

created_at: Field.datetime({
  label: 'Created At',
  defaultValue: 'NOW()',
  readonly: true,
}),

updated_at: Field.datetime({
  label: 'Updated At',
  defaultValue: 'NOW()',
  readonly: true,
}),

user_id: Field.text({
  label: 'User ID',
  required: true,
  maxLength: 255,
  description: 'Owner user of this preference',
}),

key: Field.text({
  label: 'Key',
  required: true,
  maxLength: 255,
  description: 'Preference key (e.g., theme, locale, plugin.ai.auto_save)',
}),

value: Field.json({
  label: 'Value',
  description: 'Preference value (any JSON-serializable type)',
}),

},

indexes: [
{ fields: ['user_id', 'key'], unique: true },
{ fields: ['user_id'] },
],

enable: {
trackHistory: false,
searchable: false,
apiEnabled: true,
apiMethods: ['get', 'list', 'create', 'update', 'delete'],
trash: false,
mru: false,
},
});

客户端使用方式

import { SystemObjectName } from '@objectstack/spec/system';

// 读取偏好
const theme = await engine.findOne(SystemObjectName.USER_PREFERENCE, {
  where: { user_id: currentUserId, key: 'theme' },
});

// 写入偏好
await engine.upsert(SystemObjectName.USER_PREFERENCE, {
  user_id: currentUserId,
  key: 'theme',
  value: JSON.stringify('dark'),
});

// 批量读取某用户所有偏好
const allPrefs = await engine.find(SystemObjectName.USER_PREFERENCE, {
  where: { user_id: currentUserId },
});