feat: add error handling for CIE authentication and improve user feedback on login page

app/pages/auth/cie/callback.vue

@@ -16,6 +16,21 @@ const state = computed(() => {
   return typeof value === 'string' ? value : ''
 })
 
+const providerError = computed(() => {
+  const value = route.query.error
+  return typeof value === 'string' ? value : ''
+})
+
+const providerCieError = computed(() => {
+  const value = route.query.cie_error
+  return typeof value === 'string' ? value : ''
+})
+
+const providerErrorDescription = computed(() => {
+  const value = route.query.error_description
+  return typeof value === 'string' ? value : ''
+})
+
 const isLoading = ref(true)
 const errorMessage = ref('')
 const statusMessage = ref('Verifica dell’autenticazione CIE in corso...')
@@ -50,6 +65,18 @@ const redirectToLoginError = async (code: string, fallbackMessage: string) => {
 }
 
 const checkSession = async () => {
+  if (providerError.value || providerCieError.value) {
+    const isCancelled = providerErrorDescription.value.toLowerCase().includes('rejected by user')
+      || providerError.value === 'access_denied'
+      || providerCieError.value === 'invalid_request'
+
+    await redirectToLoginError(
+      isCancelled ? 'cancelled' : 'failed',
+      providerErrorDescription.value || 'Autenticazione CIE non completata. Riprova dal login.'
+    )
+    return
+  }
+
   if (!state.value) {
     await redirectToLoginError('invalid_session', 'Sessione CIE non valida: parametro state mancante.')
     return