feat: 四个 Model 新增 realname_policy 字段（含 gorm 标签和中文注释）

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/model/device.go

@@ -43,6 +43,7 @@ type Device struct {
 	SoftwareVersion   string     `gorm:"column:software_version;type:varchar(100);not null;default:'';comment:固件版本号" json:"software_version"`
 	SwitchMode        string     `gorm:"column:switch_mode;type:varchar(10);not null;default:'0';comment:切卡模式：0=自动 1=手动" json:"switch_mode"`
 	LastGatewaySyncAt *time.Time `gorm:"column:last_gateway_sync_at;comment:最后一次 sync-info 同步时间" json:"last_gateway_sync_at,omitempty"`
+	RealnamePolicy    string     `gorm:"column:realname_policy;type:varchar(20);default:'none';not null;comment:实名认证策略(none=无需实名,before_order=先实名后充值/购买,after_order=先充值/购买后实名)" json:"realname_policy"`
 }
 
 // TableName 指定表名