fix: 修复 episodes + yearly_targets 模型导入缺失，增 DELETE 接口，冒烟 6/6 全绿

backend/app/api/users.py

@@ -6,7 +6,7 @@ from fastapi import APIRouter, Depends, HTTPException, status
 from sqlmodel import Session, select
 
 from app.core.deps import get_current_user, require_role
-from app.core.security import hash_password, verify_password
+from app.core.security import hash_password
 from app.db.session import get_session
 from app.models.user import User, UserRole
 from app.schemas.user_admin import UserCreate, UserResponse, UserUpdate