新增摸大红业务并修复后台链接按钮白字

支持分类筛选、搜索、下单支付建群与固定二维码；合并迁移种子数据；后台表格编辑/详情链接恢复主题色可见。

backend/internal/model/chat.go

@@ -10,6 +10,7 @@ type ChatConversation struct {
 	ID                 uint64     `gorm:"primaryKey" json:"id"`
 	OrderID            *uint64    `gorm:"uniqueIndex" json:"order_id"`
 	ListingID          *uint64    `gorm:"index" json:"listing_id"`
+	MohongOrderID      *uint64    `gorm:"column:mohong_order_id;uniqueIndex" json:"mohong_order_id"`
 	Type               string     `gorm:"size:32;not null;default:'order_group'" json:"type"`
 	Title              string     `gorm:"size:128;not null" json:"title"`
 	Status             string     `gorm:"size:32;not null;default:'active'" json:"status"`

backend/internal/model/mohong.go

@@ -0,0 +1,98 @@
+package model
+
+import (
+	"time"
+
+	"gorm.io/datatypes"
+)
+
+// MohongCategory 摸大红商品分类。
+type MohongCategory struct {
+	ID        uint64    `gorm:"primaryKey" json:"id"`
+	Name      string    `gorm:"size:64;not null;uniqueIndex" json:"name"`
+	Code      string    `gorm:"size:64;not null;default:''" json:"code"`
+	SortOrder int       `gorm:"column:sort_order;not null;default:0" json:"sort_order"`
+	Status    string    `gorm:"size:16;not null;default:'enabled'" json:"status"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
+}
+
+func (MohongCategory) TableName() string {
+	return "mohong_categories"
+}
+
+// MohongProductCategory 商品与分类多对多（同一商品可出现在大红/九格等）。
+type MohongProductCategory struct {
+	ProductID  uint64 `gorm:"column:product_id;primaryKey" json:"product_id"`
+	CategoryID uint64 `gorm:"column:category_id;primaryKey;index" json:"category_id"`
+}
+
+func (MohongProductCategory) TableName() string {
+	return "mohong_product_categories"
+}
+
+// MohongProduct 摸大红商品。
+type MohongProduct struct {
+	ID                uint64         `gorm:"primaryKey" json:"id"`
+	CategoryID        *uint64        `gorm:"column:category_id;index" json:"category_id"` // 主分类（展示用）
+	Title             string         `gorm:"size:128;not null" json:"title"`
+	CoverURL          string         `gorm:"column:cover_url;size:512;not null;default:''" json:"cover_url"`
+	ImageURLs         datatypes.JSON `gorm:"column:image_urls" json:"image_urls"`
+	Description       string         `gorm:"type:text;not null" json:"description"`
+	PriceCent         int64          `gorm:"column:price_cent;not null;default:0" json:"-"`
+	OriginalPriceCent int64          `gorm:"column:original_price_cent;not null;default:0" json:"-"`
+	Unit              string         `gorm:"size:32;not null;default:'份'" json:"unit"`
+	Stock             int            `gorm:"not null;default:-1" json:"stock"`
+	SortOrder         int            `gorm:"column:sort_order;not null;default:0" json:"sort_order"`
+	Status            string         `gorm:"size:16;not null;default:'draft'" json:"status"`
+	QrcodeImageURL    string         `gorm:"column:qrcode_image_url;size:512;not null;default:''" json:"qrcode_image_url"`
+	CreatedBy         *uint64        `gorm:"column:created_by" json:"created_by"`
+	CreatedAt         time.Time      `json:"created_at"`
+	UpdatedAt         time.Time      `json:"updated_at"`
+}
+
+func (MohongProduct) TableName() string {
+	return "mohong_products"
+}
+
+// MohongOrder 摸大红订单。
+type MohongOrder struct {
+	ID                uint64         `gorm:"primaryKey" json:"id"`
+	OrderNo           string         `gorm:"size:64;not null;uniqueIndex" json:"order_no"`
+	UserID            uint64         `gorm:"not null;index" json:"user_id"`
+	ProductID         uint64         `gorm:"not null;index" json:"product_id"`
+	Quantity          int            `gorm:"not null;default:1" json:"quantity"`
+	UnitPriceCent     int64          `gorm:"column:unit_price_cent;not null;default:0" json:"-"`
+	AmountCent        int64          `gorm:"column:amount_cent;not null;default:0" json:"-"`
+	Status            string         `gorm:"size:32;not null;default:'pending_payment';index" json:"status"`
+	ProductSnapshot   datatypes.JSON `gorm:"column:product_snapshot" json:"product_snapshot"`
+	QrcodeURLSnapshot string         `gorm:"column:qrcode_url_snapshot;size:512;not null;default:''" json:"qrcode_url_snapshot"`
+	CopyText          string         `gorm:"type:text;not null" json:"copy_text"`
+	ConversationID    *uint64        `gorm:"column:conversation_id" json:"conversation_id"`
+	PaidAt            *time.Time     `json:"paid_at"`
+	CompletedAt       *time.Time     `json:"completed_at"`
+	CancelledAt       *time.Time     `json:"cancelled_at"`
+	CancelReason      string         `gorm:"size:255;not null;default:''" json:"cancel_reason"`
+	AdminRemark       string         `gorm:"size:255;not null;default:''" json:"admin_remark"`
+	CreatedAt         time.Time      `json:"created_at"`
+	UpdatedAt         time.Time      `json:"updated_at"`
+}
+
+func (MohongOrder) TableName() string {
+	return "mohong_orders"
+}
+
+const (
+	MohongCategoryStatusEnabled  = "enabled"
+	MohongCategoryStatusDisabled = "disabled"
+
+	MohongProductStatusDraft   = "draft"
+	MohongProductStatusOnSale  = "on_sale"
+	MohongProductStatusOffSale = "off_sale"
+
+	MohongOrderStatusPendingPayment = "pending_payment"
+	MohongOrderStatusPaid           = "paid"
+	MohongOrderStatusCompleted      = "completed"
+	MohongOrderStatusCancelled      = "cancelled"
+	MohongOrderStatusRefunded       = "refunded"
+)