feat: Implement role-based access control (RBAC) with 3-tier authorization

- Add 3 user roles: user, admin, super_admin
- Restrict LLM config management to super_admin only
- Restrict audit logs and statistics to super_admin only
- Update AdminPage with role-based tab visibility
- Add complete 5 Why prompt from 5why-analyzer.jsx
- Add system documentation and authorization guide
- Add ErrorModal component and seed test users script

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/api.js

@@ -31,7 +31,10 @@ class ApiClient {
 
       return data;
     } catch (error) {
-      console.error('API Error:', error);
+      // 只對非認證錯誤顯示控制台訊息
+      if (!endpoint.includes('/auth/me') || !error.message.includes('未登入')) {
+        console.error('API Error:', error);
+      }
       throw error;
     }
   }