sequenceDiagram
    participant U as 管理员浏览器
    participant G as Gin Router
    participant MW as AuthMiddleware
    participant H as HandlerCards
    participant CM as CardModel

    Note over U,CM: 卡片列表
    U->>G: GET /admin/cards
    G->>MW: AuthRequired()
    MW->>MW: 检查 Cookie session_id
    alt 未登录
        MW-->>U: 302 → /admin/login
    else 已登录
        MW->>H: CardsList(c)
        H->>CM: GetAllCards()
        CM-->>H: []Card
        H-->>U: 卡片列表 HTML
    end

    Note over U,CM: 新增卡片
    U->>G: GET /admin/cards/new
    G->>H: CardCreateGet(c)
    H-->>U: 空表单 HTML

    U->>G: POST /admin/cards {icon, title, subtitle, url}
    G->>H: CardCreatePost(c)
    H->>CM: CreateCard(&Card{...})
    CM->>CM: INSERT INTO cards(...)
    CM-->>H: nil
    H-->>U: 302 Redirect → /admin/cards

    Note over U,CM: 编辑卡片
    U->>G: GET /admin/cards/:id/edit
    G->>H: CardEditGet(c)
    H->>CM: GetCardByID(id)
    CM-->>H: *Card
    H-->>U: 预填表单 HTML

    U->>G: POST /admin/cards/:id {icon, title, subtitle, url}
    G->>H: CardEditPost(c)
    H->>CM: UpdateCard(&Card{...})
    CM->>CM: UPDATE cards SET ... WHERE id=?
    CM-->>H: nil
    H-->>U: 302 Redirect → /admin/cards

    Note over U,CM: 删除卡片
    U->>G: POST /admin/cards/:id/delete
    G->>H: CardDelete(c)
    H->>CM: DeleteCard(id)
    CM->>CM: DELETE FROM cards WHERE id=?
    CM-->>H: nil
    H-->>U: 302 Redirect → /admin/cards