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/app/models/user.py

@@ -0,0 +1,55 @@
+from datetime import datetime, timezone
+from typing import Optional
+
+from beanie import Document
+from pymongo import IndexModel, ASCENDING
+from pydantic import BaseModel, Field
+
+
+class EmergencyContact(BaseModel):
+    name: str = ""
+    relation: str = ""
+    phone: str = ""
+
+
+class User(Document):
+    openid: str = Field(..., unique=True)
+    union_id: Optional[str] = None
+    session_key: Optional[str] = None
+
+    # Basic info
+    name: str = ""
+    phone: Optional[str] = None
+    age: Optional[int] = None
+    height: Optional[float] = None  # cm
+    pre_pregnancy_weight: Optional[float] = None  # kg
+    current_weight: Optional[float] = None  # kg
+    blood_type: Optional[str] = None
+    allergies: list[str] = Field(default_factory=list)
+    medical_history: list[str] = Field(default_factory=list)
+
+    # Pregnancy info
+    last_period_date: Optional[datetime] = None
+    due_date: Optional[datetime] = None
+    pregnancy_week: Optional[int] = None
+    pregnancy_day: Optional[int] = None
+    multiple_pregnancy: Optional[str] = None  # 单胎/双胎/三胎+
+    pregnancy_count: Optional[int] = None  # 第几次怀孕
+
+    emergency_contact: EmergencyContact = Field(default_factory=EmergencyContact)
+
+    # Status
+    is_onboarded: bool = False
+    avatar_url: Optional[str] = None
+    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+    updated_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+
+    class Settings:
+        name = "users"
+        indexes = [
+            IndexModel(
+                [("phone", ASCENDING)],
+                unique=True,
+                partialFilterExpression={"phone": {"$type": "string"}},
+            ),
+        ]