init: 初始化 AssetX 项目仓库

包含 webapp（Next.js 用户端）、webapp-back（Go 后端）、
antdesign（管理后台）、landingpage（营销落地页）、
数据库 SQL 和配置文件。

webapp-back/models/collateral_buy.go

@@ -0,0 +1,22 @@
+package models
+
+import "time"
+
+// CollateralBuyRecord records each collateral purchase made by the buyer bot
+type CollateralBuyRecord struct {
+	ID             uint      `gorm:"primaryKey;autoIncrement" json:"id"`
+	ChainID        int       `gorm:"index" json:"chain_id"`
+	TxHash         string    `gorm:"size:66;uniqueIndex" json:"tx_hash"`
+	BuyerAddr      string    `gorm:"size:42" json:"buyer_addr"`
+	AssetAddr      string    `gorm:"size:42;index" json:"asset_addr"`
+	AssetSymbol    string    `gorm:"size:50" json:"asset_symbol"`
+	PaidAmount     string    `gorm:"size:78" json:"paid_amount"`     // USDC paid, base units
+	ReceivedAmount string    `gorm:"size:78" json:"received_amount"` // collateral received, base units
+	GasUsed        uint64    `json:"gas_used"`
+	BlockNumber    uint64    `json:"block_number"`
+	Status         string    `gorm:"size:20;default:'success'" json:"status"` // success / failed
+	ErrorMessage   string    `gorm:"type:text" json:"error_message,omitempty"`
+	CreatedAt      time.Time `json:"created_at"`
+}
+
+func (CollateralBuyRecord) TableName() string { return "collateral_buy_records" }