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/models/audit_log.py

@@ -0,0 +1,53 @@
+from enum import Enum
+
+from sqlalchemy import Integer, JSON, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.models.base import BaseModel
+
+
+class AuditAction(str, Enum):
+    """审计操作类型"""
+    CREATE = "CREATE"
+    UPDATE = "UPDATE"
+    DELETE = "DELETE"
+    VIEW = "VIEW"
+    EXPORT = "EXPORT"
+    LOGIN = "LOGIN"
+    LOGOUT = "LOGOUT"
+    UPLOAD = "UPLOAD"
+    DOWNLOAD = "DOWNLOAD"
+
+
+class AuditLog(BaseModel):
+    """
+    审计日志模型
+    记录所有关键业务操作
+    
+    Attributes:
+        company_id: 企业 ID
+        user_id: 用户 ID
+        action: 操作类型
+        resource_type: 资源类型 (如 company, user, task, file)
+        resource_id: 资源 ID
+        details: 操作详情 (JSON)
+        ip_address: IP 地址
+        user_agent: User-Agent
+    """
+    
+    __tablename__ = "audit_logs"
+
+    company_id: Mapped[int] = mapped_column(Integer, nullable=False, index=True)
+    user_id: Mapped[int | None] = mapped_column(Integer, nullable=True, index=True)
+    action: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
+    resource_type: Mapped[str] = mapped_column(String(100), nullable=False, index=True)
+    resource_id: Mapped[str | None] = mapped_column(String(200), nullable=True, index=True)
+    details: Mapped[dict | None] = mapped_column(JSON, nullable=True)
+    ip_address: Mapped[str | None] = mapped_column(String(50), nullable=True)
+    user_agent: Mapped[str | None] = mapped_column(Text, nullable=True)
+
+    def __repr__(self) -> str:
+        return (
+            f"<AuditLog(id={self.id}, company_id={self.company_id}, "
+            f"action='{self.action}', resource_type='{self.resource_type}')>"
+        )