feat: 实现分类管理功能，包括数据模型、仓库层、服务层和数据库初始化脚本

internal/models/default_category.go

@@ -0,0 +1,106 @@
+package models
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+)
+
+// DefaultCategory represents a category template for new user initialization
+// These templates are copied to users' categories table when they first access categories
+type DefaultCategory struct {
+	ID        uint         `gorm:"primarykey" json:"id"`
+	Name      string       `gorm:"size:50;not null" json:"name"`
+	Icon      string       `gorm:"size:100" json:"icon"`         // Iconify format: mdi:icon-name
+	Color     string       `gorm:"size:20" json:"color"`         // HEX color code (e.g., #FF6B35)
+	Type      CategoryType `gorm:"size:20;not null" json:"type"` // income or expense
+	ParentID  *uint        `gorm:"index" json:"parent_id,omitempty"`
+	SortOrder int          `gorm:"default:0" json:"sort_order"`
+	IsActive  bool         `gorm:"default:true" json:"is_active"`
+	CreatedAt time.Time    `json:"created_at"`
+	UpdatedAt time.Time    `json:"updated_at"`
+
+	// Relationships
+	Parent   *DefaultCategory  `gorm:"foreignKey:ParentID" json:"parent,omitempty"`
+	Children []DefaultCategory `gorm:"foreignKey:ParentID" json:"children,omitempty"`
+}
+
+// TableName specifies the table name for DefaultCategory
+func (DefaultCategory) TableName() string {
+	return "default_categories"
+}
+
+// GetAllDefaultCategories retrieves all active default categories from the database
+func GetAllDefaultCategories(db *gorm.DB) ([]DefaultCategory, error) {
+	var categories []DefaultCategory
+	err := db.Where("is_active = ?", true).Order("sort_order ASC").Find(&categories).Error
+	return categories, err
+}
+
+// GetDefaultCategoriesWithChildren retrieves all active root categories with their children
+func GetDefaultCategoriesWithChildren(db *gorm.DB) ([]DefaultCategory, error) {
+	var categories []DefaultCategory
+	err := db.Where("is_active = ? AND parent_id IS NULL", true).
+		Preload("Children", "is_active = ?", true).
+		Order("sort_order ASC").
+		Find(&categories).Error
+	return categories, err
+}
+
+// CopyToUserCategories copies default categories to a user's categories
+// Returns a map of old DefaultCategory ID to new Category ID for parent-child mapping
+func CopyDefaultCategoriesToUser(db *gorm.DB, userID uint) error {
+	// Get all default categories
+	var defaults []DefaultCategory
+	if err := db.Where("is_active = ?", true).Order("sort_order ASC").Find(&defaults).Error; err != nil {
+		return err
+	}
+
+	if len(defaults) == 0 {
+		return nil // No default categories to copy
+	}
+
+	// Map to track old ID -> new ID for parent references
+	idMap := make(map[uint]uint)
+
+	// First pass: create all root categories (no parent)
+	for _, dc := range defaults {
+		if dc.ParentID == nil {
+			cat := Category{
+				UserID:    userID,
+				Name:      dc.Name,
+				Icon:      dc.Icon,
+				Color:     dc.Color,
+				Type:      dc.Type,
+				ParentID:  nil,
+				SortOrder: dc.SortOrder,
+			}
+			if err := db.Create(&cat).Error; err != nil {
+				return err
+			}
+			idMap[dc.ID] = cat.ID
+		}
+	}
+
+	// Second pass: create all child categories
+	for _, dc := range defaults {
+		if dc.ParentID != nil {
+			newParentID := idMap[*dc.ParentID]
+			cat := Category{
+				UserID:    userID,
+				Name:      dc.Name,
+				Icon:      dc.Icon,
+				Color:     dc.Color,
+				Type:      dc.Type,
+				ParentID:  &newParentID,
+				SortOrder: dc.SortOrder,
+			}
+			if err := db.Create(&cat).Error; err != nil {
+				return err
+			}
+			idMap[dc.ID] = cat.ID
+		}
+	}
+
+	return nil
+}