feat: 新用户默认昵称及个人中心加载状态修复

- 新用户注册时随机生成普拉提主题默认昵称（16 个可选）
- 修复 App 启动后个人中心首次进入不展示用户信息的 bug
  - loggedIn 改为仅依赖 token 是否存在
  - 新增 hasProfile 判断用户数据是否已加载
  - 未加载时显示骨架屏而非空白
- 抽离随机函数为可注入依赖，消除 Math.random 测试耦合

packages/server/src/auth/auth.service.ts

@@ -1,4 +1,4 @@
-import { Injectable, UnauthorizedException } from '@nestjs/common'
+import { Inject, Injectable, UnauthorizedException } from '@nestjs/common'
 import { JwtService } from '@nestjs/jwt'
 import { User } from '@prisma/client'
 import { UserRole } from '@mp-pilates/shared'
@@ -22,12 +22,39 @@ export interface JwtPayload {
  */
 const sessionKeyStore = new Map<string, string>()
 
+export const RANDOM_FN_TOKEN = 'RANDOM_FN_TOKEN'
+
+const DEFAULT_NICKNAMES = [
+  '优雅普拉提',
+  '柔韧时光',
+  '轻盈姿态',
+  '身心合一',
+  '舒展生活',
+  '静享流动',
+  '普拉提修行者',
+  '姿态雕塑师',
+  '呼吸艺术家',
+  '柔美力量',
+  '线条雕刻师',
+  '优雅行者',
+  '轻盈韵律',
+  '内在平和',
+  '舒展之美',
+]
+
+function generateDefaultNickname(
+  randomFn: () => number = Math.random,
+): string {
+  return DEFAULT_NICKNAMES[Math.floor(randomFn() * DEFAULT_NICKNAMES.length)]
+}
+
 @Injectable()
 export class AuthService {
   constructor(
     private readonly prisma: PrismaService,
     private readonly jwtService: JwtService,
     private readonly wechatService: WechatService,
+    @Inject(RANDOM_FN_TOKEN) private readonly randomFn: () => number = Math.random,
   ) {}
 
   async login(code: string): Promise<LoginResult> {
@@ -44,6 +71,7 @@ export class AuthService {
         data: {
           openid,
           ...(unionid !== undefined && { unionid }),
+          nickname: generateDefaultNickname(this.randomFn),
         },
       }))