fix(usage): correct selectedTemplate initialization logic

Previously, selectedTemplate was initialized to null when no NEW_API
credentials were detected, which caused the credentials config section
to be hidden even for new configurations or GENERAL template users.

Now properly detects:
- NEW_API template (has accessToken or userId)
- GENERAL template (has apiKey or baseUrl)
- Default to GENERAL for new configurations (matches default code template)

src/components/UsageScriptModal.tsx

@@ -176,10 +176,16 @@ const UsageScriptModal: React.FC<UsageScriptModalProps> = ({
   const [selectedTemplate, setSelectedTemplate] = useState<string | null>(
     () => {
       const existingScript = provider.meta?.usage_script;
+      // 检测 NEW_API 模板（有 accessToken 或 userId）
       if (existingScript?.accessToken || existingScript?.userId) {
         return TEMPLATE_KEYS.NEW_API;
       }
-      return null;
+      // 检测 GENERAL 模板（有 apiKey 或 baseUrl）
+      if (existingScript?.apiKey || existingScript?.baseUrl) {
+        return TEMPLATE_KEYS.GENERAL;
+      }
+      // 新配置或无凭证：默认使用 GENERAL（与默认代码模板一致）
+      return TEMPLATE_KEYS.GENERAL;
     },
   );