chore(frontend): 移除未使用的新手引导组件残留代码

删除开发过程中遗留的未使用文件：
- TourDescription.vue: 未被使用的结构化描述组件
- useTourStepDescription.ts: 步骤key映射，引用的组件从未创建
- TourStepDescriptions/: 空的组件目录

当前实现通过 i18n + HTML 字符串直接提供描述内容，无需这些文件。

frontend/src/composables/useTourStepDescription.ts

@@ -1,79 +0,0 @@
-export const ADMIN_TOUR_STEP_KEYS = [
-  'admin.welcome',
-  'admin.groupManage',
-  'admin.createGroup',
-  'admin.groupName',
-  'admin.groupPlatform',
-  'admin.groupMultiplier',
-  'admin.groupExclusive',
-  'admin.groupSubmit',
-  'admin.accountManage',
-  'admin.createAccount',
-  'admin.accountName',
-  'admin.accountPlatform',
-  'admin.accountType',
-  'admin.accountPriority',
-  'admin.accountGroups',
-  'admin.accountSubmit',
-  'admin.keyManage',
-  'admin.createKey',
-  'admin.keyName',
-  'admin.keyGroup',
-  'admin.keySubmit'
-] as const
-
-export const USER_TOUR_STEP_KEYS = [
-  'user.welcome',
-  'user.keyManage',
-  'user.createKey',
-  'user.keyName',
-  'user.keyGroup',
-  'user.keySubmit'
-] as const
-
-export const TOUR_STEP_KEYS = [...ADMIN_TOUR_STEP_KEYS, ...USER_TOUR_STEP_KEYS] as const
-
-export type TourStepKey = (typeof TOUR_STEP_KEYS)[number]
-
-export const TOUR_STEP_COMPONENTS: Record<TourStepKey, string> = {
-  'admin.welcome': 'AdminWelcomeDescription',
-  'admin.groupManage': 'AdminGroupManageDescription',
-  'admin.createGroup': 'AdminCreateGroupDescription',
-  'admin.groupName': 'AdminGroupNameDescription',
-  'admin.groupPlatform': 'AdminGroupPlatformDescription',
-  'admin.groupMultiplier': 'AdminGroupMultiplierDescription',
-  'admin.groupExclusive': 'AdminGroupExclusiveDescription',
-  'admin.groupSubmit': 'AdminGroupSubmitDescription',
-  'admin.accountManage': 'AdminAccountManageDescription',
-  'admin.createAccount': 'AdminCreateAccountDescription',
-  'admin.accountName': 'AdminAccountNameDescription',
-  'admin.accountPlatform': 'AdminAccountPlatformDescription',
-  'admin.accountType': 'AdminAccountTypeDescription',
-  'admin.accountPriority': 'AdminAccountPriorityDescription',
-  'admin.accountGroups': 'AdminAccountGroupsDescription',
-  'admin.accountSubmit': 'AdminAccountSubmitDescription',
-  'admin.keyManage': 'AdminKeyManageDescription',
-  'admin.createKey': 'AdminCreateKeyDescription',
-  'admin.keyName': 'AdminKeyNameDescription',
-  'admin.keyGroup': 'AdminKeyGroupDescription',
-  'admin.keySubmit': 'AdminKeySubmitDescription',
-  'user.welcome': 'UserWelcomeDescription',
-  'user.keyManage': 'UserKeyManageDescription',
-  'user.createKey': 'UserCreateKeyDescription',
-  'user.keyName': 'UserKeyNameDescription',
-  'user.keyGroup': 'UserKeyGroupDescription',
-  'user.keySubmit': 'UserKeySubmitDescription'
-}
-
-export const useTourStepDescription = () => {
-  const getComponentName = (stepKey: TourStepKey) => TOUR_STEP_COMPONENTS[stepKey]
-
-  const isTourStepKey = (value: string): value is TourStepKey =>
-    Object.prototype.hasOwnProperty.call(TOUR_STEP_COMPONENTS, value)
-
-  return {
-    getComponentName,
-    isTourStepKey,
-    stepKeys: TOUR_STEP_KEYS
-  }
-}