feat: 初始化孕育无忧全栈项目基础代码结构

完成项目初始搭建，包含后端FastAPI+MongoDB服务、前端React+Vite项目的完整基础结构，添加各类配置文件与依赖清单，涵盖核心业务初始框架。

backend/scripts/cleanup_demo_users.py

@@ -0,0 +1,47 @@
+"""
+清理旧的共享 demo_web_user 及其关联数据。
+
+部署新版 demo 登录逻辑后运行一次即可：
+    python -m scripts.cleanup_demo_users
+"""
+
+import asyncio
+
+from motor.motor_asyncio import AsyncIOMotorClient
+from beanie import init_beanie
+
+from app.config import Settings
+from app.models.user import User
+from app.models.report import Report
+from app.models.analysis import Analysis
+from app.models.chat import ChatSession
+from app.models.checkup import CheckupPlan
+
+
+async def main():
+    settings = Settings()
+    client = AsyncIOMotorClient(settings.mongodb_url)
+    db = client[settings.database_name]
+    await init_beanie(database=db, document_models=[User, Report, Analysis, ChatSession, CheckupPlan])
+
+    user = await User.find_one(User.openid == "demo_web_user")
+    if not user:
+        print("未找到 demo_web_user，无需清理。")
+        return
+
+    uid = user.id
+    r = await Report.find(Report.user_id == uid).delete()
+    a = await Analysis.find(Analysis.user_id == uid).delete()
+    c = await ChatSession.find(ChatSession.user_id == uid).delete()
+    p = await CheckupPlan.find(CheckupPlan.user_id == uid).delete()
+    await user.delete()
+
+    print(f"已清理 demo_web_user (id={uid}):")
+    print(f"  Reports:      {r.deleted_count if r else 0}")
+    print(f"  Analyses:     {a.deleted_count if a else 0}")
+    print(f"  ChatSessions: {c.deleted_count if c else 0}")
+    print(f"  CheckupPlans: {p.deleted_count if p else 0}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())