feat: 初始化考培练系统项目

- 从服务器拉取完整代码
- 按框架规范整理项目结构
- 配置 Drone CI 测试环境部署
- 包含后端(FastAPI)、前端(Vue3)、管理端

技术栈: Vue3 + TypeScript + FastAPI + MySQL

backend/app/models/position_member.py

@@ -0,0 +1,26 @@
+"""
+岗位成员关联模型
+"""
+from datetime import datetime
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Boolean, UniqueConstraint, func
+from sqlalchemy.orm import relationship
+from app.models.base import BaseModel, SoftDeleteMixin
+
+
+class PositionMember(BaseModel, SoftDeleteMixin):
+    """岗位成员关联表"""
+    __tablename__ = "position_members"
+    
+    # 添加唯一约束：同一岗位下同一用户只能有一条有效记录
+    __table_args__ = (
+        UniqueConstraint('position_id', 'user_id', 'is_deleted', name='uix_position_user'),
+    )
+    
+    position_id = Column(Integer, ForeignKey("positions.id"), nullable=False, comment="岗位ID")
+    user_id = Column(Integer, ForeignKey("users.id"), nullable=False, comment="用户ID")
+    role = Column(String(50), comment="成员角色（预留字段）")
+    joined_at = Column(DateTime, server_default=func.now(), comment="加入时间（北京时间）")
+    
+    # 关系
+    position = relationship("Position", back_populates="members")
+    user = relationship("User", back_populates="position_memberships")