fix: align qwen balance signing/query encoding to avoid 400

modules/balance_client.py

@@ -161,7 +161,10 @@ def fetch_qwen_balance() -> Dict[str, Any]:
     }
     signature = _sign(params, sk)
     params["Signature"] = signature
-    url = "https://bss.aliyuncs.com/?" + parse.urlencode(params)
+
+    # 按阿里云规范组装最终查询字符串（不可用 urlencode 的 quote_plus）
+    query = "&".join(f"{_percent_encode(k)}={_percent_encode(v)}" for k, v in params.items())
+    url = "https://bss.aliyuncs.com/?" + query
 
     payload, err = _http_get(url)
     if err: