fix: 修复授信表单提交 - 使用submit_url替代url, 移除手动buttons

- url → submit_url (Form正确的属性名)
- 移除手动buttons配置 (Form自动生成Submit/Reset工具栏)
- 移除method:POST (Form默认POST)

wwwroot/credit_limit/api/set_credit_form.ui

@@ -4,8 +4,7 @@
     "options": {
         "width": "100%",
         "padding": "16px",
-        "url": "{{entire_url('/accounting/credit_limit/api/set_customer_credit.dspy')}}",
-        "method": "POST",
+        "submit_url": "{{entire_url('/accounting/credit_limit/api/set_customer_credit.dspy')}}",
         "fields": [
             {
                 "name": "id",
@@ -46,32 +45,6 @@
                 "uitype": "str",
                 "value": "{{params_kw.get('remark', '')}}"
             }
-        ],
-        "buttons": [
-            {
-                "label": "保存",
-                "actiontype": "submit",
-                "bgcolor": "#3B82F6",
-                "color": "#FFFFFF",
-                "binds": [{
-                    "wid": "self",
-                    "event": "click",
-                    "actiontype": "submit",
-                    "target": "credit_form"
-                }]
-            },
-            {
-                "label": "取消",
-                "actiontype": "close",
-                "bgcolor": "#475569",
-                "color": "#FFFFFF",
-                "binds": [{
-                    "wid": "self",
-                    "event": "click",
-                    "actiontype": "close",
-                    "target": "PopupWindow"
-                }]
-            }
         ]
     },
     "binds": [{