classDiagram
    class Tag {
        +int id
        +int user_id
        +string name
        +string color
        +string created_at
    }

    class TransactionTag {
        +int transaction_id
        +int tag_id
    }

    class Transaction {
        +int id
        +int user_id
        +int amount
        +string type
        +int category_id
        +string note
        +string date
        +int group_id
        +int recurring_id
        +Tag[] tags
    }

    class Feedback {
        +int id
        +int user_id
        +string type
        +string content
        +string contact
        +string status
        +string admin_reply
        +string created_at
    }

    class Category {
        +int id
        +int user_id
        +string name
        +string icon
        +string color
        +string type
        +int sort_order
        +int is_custom
    }

    Transaction "1" --o "*" TransactionTag : has
    Tag "1" --o "*" TransactionTag : referenced_by
    Transaction ..> Category : belongs_to

    note for Tag "每用户最多 20 个标签\n8 色预设颜色选择器\n标签不区分收支类型"
    note for TransactionTag "复合主键 (transaction_id, tag_id)\n每笔交易最多 5 个标签"