feat: 添加文档管理系统前后端基础功能

- 新增后端FastAPI应用，包含用户管理、文档管理和操作日志功能
- 实现JWT认证机制，支持用户注册、登录、登出操作
- 添加数据库模型定义，包括用户表、文档表和操作日志表
- 实现文档的增删改查功能及权限控制
- 添加管理员功能，支持用户管理和全局操作日志查看
- 新增前端界面，实现完整的用户交互体验
- 配置环境变量示例和Git忽略规则
- 编写详细的README文档，包含安装和使用说明

models.py

@@ -0,0 +1,52 @@
+from sqlalchemy import Column, Integer, String, Text, DateTime, Boolean, ForeignKey
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from database import Base
+
+class User(Base):
+    __tablename__ = "users"
+    
+    id = Column(Integer, primary_key=True, index=True)
+    username = Column(String(50), unique=True, index=True, nullable=False)
+    email = Column(String(100), unique=True, index=True, nullable=False)
+    hashed_password = Column(String(255), nullable=False)
+    full_name = Column(String(100), nullable=True)
+    is_admin = Column(Boolean, default=False)
+    is_active = Column(Boolean, default=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    
+    # 关系
+    documents = relationship("Document", back_populates="owner")
+    operation_logs = relationship("UserOperationLog", back_populates="user")
+
+class Document(Base):
+    __tablename__ = "documents"
+    
+    id = Column(Integer, primary_key=True, index=True)
+    title = Column(String(200), nullable=False)
+    content = Column(Text, nullable=True)
+    description = Column(String(500), nullable=True)
+    file_type = Column(String(50), default="txt")  # txt, pdf, doc, etc.
+    file_size = Column(Integer, default=0)  # 文件大小（字节）
+    is_public = Column(Boolean, default=False)
+    owner_id = Column(Integer, ForeignKey("users.id"))
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+    
+    # 关系
+    owner = relationship("User", back_populates="documents")
+
+class UserOperationLog(Base):
+    __tablename__ = "user_operation_logs"
+    
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id"))
+    operation = Column(String(100), nullable=False)  # 操作类型
+    details = Column(Text, nullable=True)  # 操作详情
+    ip_address = Column(String(50), nullable=True)  # IP地址
+    user_agent = Column(String(500), nullable=True)  # 用户代理
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    
+    # 关系
+    user = relationship("User", back_populates="operation_logs")