feat: 完善前后端核心功能模块

后端:
- 新增认证(auth)、任务(tasks)、映射(mappings)、对账(reconciliation)、异常(exceptions)、导出(exports) API
- 新增核心模块: database, security, permissions, tenant, exceptions, error_handlers
- 新增数据模型: user, company, reconciliation_task, field_mapping, uploaded_file 等
- 新增服务层: ai_recognizer, file_parser, file_storage, mapping, reconciliation 等
- 添加数据库迁移脚本

前端:
- 新增登录页面和仪表盘页面
- 新增任务列表、任务详情、字段映射页面
- 新增异常处理页面和规则设置页面
- 新增 API 代理路由 /api/[...path]
- 新增 UI 组件库 (button, card, dialog, input, table 等)
- 新增 auth 组件 (ProtectedRoute, PermissionGate)
- 新增 layout 组件 (Header, Sidebar)
- 新增 mapping 组件 (FieldMappingTable, AISuggestionPanel)
- 新增 API 客户端和 hooks (useAsync, useToast, usePermission 等)
- 新增状态管理 (auth-store, company-store, ui-store)
- 集成 Tailwind CSS 和 shadcn/ui 组件库

其他:
- 添加 Alembic 数据库迁移配置
- 添加初始化示例数据脚本
- 更新项目文档

backend/app/schemas/user.py

@@ -0,0 +1,56 @@
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, ConfigDict, EmailStr, Field
+
+
+class UserBase(BaseModel):
+    """User 基础 Schema"""
+    email: EmailStr = Field(..., description="邮箱")
+    full_name: str = Field(..., min_length=1, max_length=100, description="姓名")
+    role: str = Field(default="会计", description="角色")
+
+
+class UserCreate(UserBase):
+    """创建用户的 Schema"""
+    password: str = Field(..., min_length=6, max_length=50, description="密码")
+    company_id: int = Field(..., description="企业ID")
+
+
+class UserUpdate(BaseModel):
+    """更新用户的 Schema"""
+    full_name: Optional[str] = Field(None, min_length=1, max_length=100)
+    role: Optional[str] = None
+    permissions: Optional[dict] = None
+    status: Optional[str] = None
+
+
+class UserResponse(UserBase):
+    """用户响应 Schema"""
+    model_config = ConfigDict(from_attributes=True)
+    
+    id: int
+    company_id: int
+    status: str
+    permissions: Optional[dict]
+    last_login_at: Optional[datetime]
+    created_at: datetime
+    updated_at: datetime
+
+
+class UserLogin(BaseModel):
+    """用户登录 Schema"""
+    email: EmailStr = Field(..., description="邮箱")
+    password: str = Field(..., description="密码")
+
+
+class Token(BaseModel):
+    """Token Schema"""
+    access_token: str
+    token_type: str = "bearer"
+
+
+class TokenData(BaseModel):
+    """Token 数据 Schema"""
+    user_id: Optional[int] = None
+    email: Optional[str] = None