Fix React error #130 by correcting Card component usage

- Fixed all Card components to use padding prop instead of className
- Updated padding values: p-4 -> sm, p-6 -> md, p-8 -> lg
- This resolves the React element type invalid error

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/services/settings.service.ts

@@ -72,6 +72,11 @@ export const settingsService = {
     await api.put('/api/admin/settings/theme', settings);
   },
 
+  // Update multiple settings at once
+  async updateSettings(settings: Record<string, any>): Promise<void> {
+    await api.put('/api/admin/settings', settings);
+  },
+
   // Get storage information
   async getStorageInfo(): Promise<StorageInfo> {
     const response = await api.get<StorageInfo>('/api/admin/settings/storage/info');