refactor: centralize validation, error handling, and formatting logic

Extract shared auth logic and validation rules to shared/auth.ts
Introduce utility functions for HTTP errors and user input parsing
Standardize error messages and date formatting across the app

app/pages/security/index.vue

@@ -87,7 +87,7 @@
                       {{ passkey.label }}
                     </div>
                     <div class="text-sm text-muted">
-                      Added {{ formatDate(passkey.createdAt) }}
+                      Added {{ formatDateTime(passkey.createdAt) }}
                     </div>
                   </div>
 
@@ -105,7 +105,10 @@
 <script lang="ts" setup>
 import type { FormError, FormSubmitEvent } from '@nuxt/ui'
 
-import { MIN_PASSWORD_LENGTH, type PasskeySummary } from '~~/shared/auth'
+import { getDefaultAuthenticatedPath, MIN_PASSWORD_LENGTH, type PasskeySummary } from '~~/shared/auth'
+
+import { getErrorMessage } from '../../utils/errors'
+import { formatDateTime } from '../../utils/formatters'
 
 definePageMeta({
   middleware: 'auth'
@@ -152,8 +155,8 @@ async function fetchPasskeys() {
 }
 
 function maybeRedirectAfterOnboarding(previouslyRequired: boolean) {
-  if (previouslyRequired && !auth.needsOnboarding.value) {
-    router.push(auth.isSuperAdmin.value ? '/management/users' : '/security')
+  if (previouslyRequired && auth.user.value && !auth.needsOnboarding.value) {
+    router.push(getDefaultAuthenticatedPath(auth.user.value))
   }
 }
 
@@ -192,7 +195,7 @@ async function changePassword(event: FormSubmitEvent<typeof passwordForm>) {
   } catch (error: any) {
     toast.add({
       title: 'Password update failed',
-      description: error?.data?.statusMessage || 'Unable to update your password.',
+      description: getErrorMessage(error, 'Unable to update your password.'),
       color: 'error',
       icon: 'i-lucide-circle-alert'
     })
@@ -246,7 +249,7 @@ async function registerPasskey() {
   } catch (error: any) {
     toast.add({
       title: 'Passkey registration failed',
-      description: error?.data?.statusMessage || error?.message || 'Unable to register a passkey.',
+      description: getErrorMessage(error, 'Unable to register a passkey.'),
       color: 'error',
       icon: 'i-lucide-circle-alert'
     })
@@ -254,15 +257,4 @@ async function registerPasskey() {
     passkeyPending.value = false
   }
 }
-
-function formatDate(value: string | null) {
-  if (!value) {
-    return 'Not available'
-  }
-
-  return new Intl.DateTimeFormat('en-MY', {
-    dateStyle: 'medium',
-    timeStyle: 'short'
-  }).format(new Date(value))
-}
 </script>