refactor: 统一状态名称映射为公共函数，清理废弃换卡/商户类型常量和模型

internal/model/financial.go

@@ -52,24 +52,3 @@ type CommissionWithdrawalSetting struct {
 func (CommissionWithdrawalSetting) TableName() string {
 	return "tb_commission_withdrawal_setting"
 }
-
-// PaymentMerchantSetting 收款商户设置模型
-// 配置支付参数(支付宝、微信等收款账户)
-type PaymentMerchantSetting struct {
-	gorm.Model
-	BaseModel     `gorm:"embedded"`
-	UserID        uint   `gorm:"column:user_id;index;not null;comment:用户ID" json:"user_id"`
-	MerchantType  string `gorm:"column:merchant_type;type:varchar(20);comment:商户类型 alipay-支付宝 wechat-微信 bank-银行卡" json:"merchant_type"`
-	AccountName   string `gorm:"column:account_name;type:varchar(255);comment:账户名称" json:"account_name"`
-	AccountNumber string `gorm:"column:account_number;type:varchar(255);comment:账号" json:"account_number"`
-	BankName      string `gorm:"column:bank_name;type:varchar(255);comment:银行名称(仅银行卡)" json:"bank_name"`
-	BankBranch    string `gorm:"column:bank_branch;type:varchar(255);comment:开户行(仅银行卡)" json:"bank_branch"`
-	IsVerified    bool   `gorm:"column:is_verified;type:boolean;default:false;comment:是否已验证" json:"is_verified"`
-	IsDefault     bool   `gorm:"column:is_default;type:boolean;default:false;comment:是否默认账户" json:"is_default"`
-	Status        int    `gorm:"column:status;type:int;default:1;comment:状态 0=禁用 1=启用" json:"status"`
-}
-
-// TableName 指定表名
-func (PaymentMerchantSetting) TableName() string {
-	return "tb_payment_merchant_setting"
-}