feat: 新增 SafeW 出站通知渠道

通过 Bot API sendMessage 投递渲染后的通知，MarkdownV2 自动转义标题与正文。

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/adapter/adapter.go

@@ -21,6 +21,8 @@ func NewSender(channelType string, smtpCfg *config.SMTPConfig, dingtalkLimiter *
 		return &WeComSender{}, nil
 	case "bark":
 		return &BarkSender{}, nil
+	case "safew":
+		return &SafeWSender{}, nil
 	case "email":
 		return NewEmailSender(*smtpCfg), nil
 	default: