新增用户管理/角色管理/菜单管理功能，修复创作流水线研究脚本

- 用户管理：新增编辑弹窗（修改用户名/角色/密码），增加组织/创建时间/最后登录列
- 角色管理：新增 Role 模型 + CRUD API，admin.html 新增角色管理 tab
- 菜单管理：新增 Menu 模型 + CRUD API，导航栏从 API 动态加载菜单项
- 个人中心：右上角下拉菜单（个人信息/修改密码/退出），新增修改密码 API
- 种子数据：initial_data.py 自动创建默认角色（admin/editor）和默认菜单（7项）
- 修复 research.py 缺少 enrich_topic_research 函数导致导入失败
- 修复 db_helper.py 中 generated_at 条件导致重创作不更新时间戳
- admin.html 操作列加宽防止按钮换行，平台配置增加删除按钮
- articles.html 预览弹窗加 lock-scroll=false 防止页面尺寸跳动

platform/backend/app/api/menu_configs.py

@@ -0,0 +1,62 @@
+from fastapi import APIRouter, Depends, HTTPException, Request
+from sqlalchemy.orm import Session
+from typing import List
+
+from ..database import get_db
+from ..models import Menu, User
+from ..schemas import MenuCreate, MenuUpdate, MenuResponse
+from .auth import get_current_admin, get_current_user
+
+router = APIRouter(prefix="/api/admin/menus", tags=["admin"])
+public_router = APIRouter(prefix="/api/menus", tags=["menus"])
+
+@router.get("", response_model=List[MenuResponse])
+def list_menus(db: Session = Depends(get_db), admin_user: User = Depends(get_current_admin)):
+    menus = db.query(Menu).order_by(Menu.sort_order).all()
+    return [MenuResponse.model_validate(m) for m in menus]
+
+@public_router.get("/active", response_model=List[MenuResponse])
+def get_active_menus(request: Request, db: Session = Depends(get_db)):
+    try:
+        user = get_current_user(request, db)
+        role = user.role
+    except Exception:
+        role = None
+    menus = db.query(Menu).filter(Menu.is_active == True).order_by(Menu.sort_order).all()
+    result = []
+    for m in menus:
+        allowed_roles = m.roles or []
+        if not allowed_roles or (role and role in allowed_roles):
+            result.append(MenuResponse.model_validate(m))
+    return result
+
+@router.post("", response_model=MenuResponse)
+def create_menu(data: MenuCreate, request: Request, db: Session = Depends(get_db), admin_user: User = Depends(get_current_admin)):
+    menu = Menu(**data.model_dump())
+    db.add(menu)
+    db.commit()
+    db.refresh(menu)
+    return MenuResponse.model_validate(menu)
+
+@router.put("/{menu_id}", response_model=MenuResponse)
+def update_menu(menu_id: int, data: MenuUpdate, request: Request, db: Session = Depends(get_db), admin_user: User = Depends(get_current_admin)):
+    menu = db.query(Menu).filter(Menu.id == menu_id).first()
+    if not menu:
+        raise HTTPException(status_code=404, detail="菜单不存在")
+    update_data = data.model_dump(exclude_unset=True)
+    for key, val in update_data.items():
+        setattr(menu, key, val)
+    db.commit()
+    db.refresh(menu)
+    return MenuResponse.model_validate(menu)
+
+@router.delete("/{menu_id}")
+def delete_menu(menu_id: int, request: Request, db: Session = Depends(get_db), admin_user: User = Depends(get_current_admin)):
+    menu = db.query(Menu).filter(Menu.id == menu_id).first()
+    if not menu:
+        raise HTTPException(status_code=404, detail="菜单不存在")
+    if menu.children:
+        raise HTTPException(status_code=400, detail="请先删除子菜单")
+    db.delete(menu)
+    db.commit()
+    return {"message": "删除成功"}