Add modular group verification system with frontend and backend checks

This commit implements a comprehensive, reusable group verification system:

Components:
- GroupCheckButton: Base component for group verification
- 7 specialized buttons: 3 real groups (authentik Admins, grupo-prueba, lvl0), 1 public access test, 2 system verification buttons
- All buttons support both frontend and backend verification modes

Backend:
- New API endpoint /api/auth/check-group for server-side group validation
- Reads Authentik headers and validates group membership

Frontend:
- Enhanced useAuthentik composable with hasGroup() and checkGroupBackend() methods
- Toast notifications for all verification results
- Smooth animations and color-coded visual feedback

UI Improvements:
- Organized layout with cards for different verification types
- Grid layout for group buttons
- Professional styling with hover effects and shadows
- Clear visual distinction between frontend/backend checks

nuxt4/app/composables/useAuthentik.ts

@@ -182,11 +182,39 @@ export const useAuthentik = () => {
     }
   }
 
+  /**
+   * Verifica si el usuario pertenece a un grupo específico (frontend)
+   * Lee los grupos desde el estado local (headers de Authentik)
+   */
+  const hasGroup = (groupName: string): boolean => {
+    if (!user.value) return false
+    return user.value.groups.includes(groupName)
+  }
+
+  /**
+   * Verifica si el usuario pertenece a un grupo específico (backend)
+   * Consulta al servidor para validar contra Authentik
+   */
+  const checkGroupBackend = async (groupName: string): Promise<boolean> => {
+    try {
+      const response = await $fetch<{ hasGroup: boolean }>(`/api/auth/check-group`, {
+        method: 'POST',
+        body: { groupName }
+      })
+      return response.hasGroup
+    } catch (error) {
+      console.error('Error checking group membership:', error)
+      return false
+    }
+  }
+
   return {
     user,
     isAuthenticated,
     logout,
     goToProfile,
-    checkSessionStatus
+    checkSessionStatus,
+    hasGroup,
+    checkGroupBackend
   }
 }