fix: resolve 'e.reduce is not a function' error in admin settings

- Remove server-side grouping logic from API response
- Return flat array instead of grouped object
- Fix data structure mismatch between API and frontend
- Resolve TypeError when accessing admin settings page

src/app/api/admin/config/route.ts

@@ -46,18 +46,8 @@ export async function GET(request: NextRequest) {
       .where(whereClause)
       .orderBy(siteConfig.key);
 
-    const groupedConfigs = configs.reduce((acc, config) => {
-      const cat = config.category;
-      if (!acc[cat]) {
-        acc[cat] = [];
-      }
-      acc[cat].push(config);
-      return acc;
-    }, {} as Record<string, typeof configs>);
-
     return success({
-      configs: groupedConfigs,
-      flat: configs,
+      configs: configs,
     });
   } catch (error) {
     return handleApiError(error);