chore: 清理敏感与开发文档，仅同步代码

- 永久忽略并从仓库移除 开发文档/
- 移除并忽略 .env 与小程序私有配置
- 同步小程序/管理端/API与脚本改动

Made-with: Cursor

soul-api/internal/wechat/transferv3/client.go

@@ -118,3 +118,11 @@ func (c *Client) GetTransferDetail(outBatchNo, outDetailNo string) ([]byte, int,
 		"/details/detail-id/" + url.PathEscape(outDetailNo)
 	return c.do("GET", path, "")
 }
+
+// GetMerchantBalance 查询商户平台账户实时余额（文档：GET /v3/merchant/fund/balance/{account_type}）
+// accountType: BASIC(基本户) | OPERATION(运营账户) | FEES(手续费账户)
+// 注意：普通商户可能需向微信申请开通权限，403 NO_AUTH 表示未开通
+func (c *Client) GetMerchantBalance(accountType string) ([]byte, int, error) {
+	path := "/v3/merchant/fund/balance/" + url.PathEscape(accountType)
+	return c.do("GET", path, "")
+}