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/login/index.vue

@@ -69,6 +69,10 @@
 <script lang="ts" setup>
 import type { FormError, FormSubmitEvent } from '@nuxt/ui'
 
+import { getDefaultAuthenticatedPath } from '~~/shared/auth'
+
+import { getErrorMessage } from '../../utils/errors'
+
 definePageMeta({
   middleware: 'guest'
 })
@@ -105,13 +109,7 @@ async function finishLogin(user: Awaited<ReturnType<typeof auth.fetchSession>>)
     return
   }
 
-  const target = user.mustChangePassword || user.needsPasskeySetup
-    ? '/security'
-    : user.role === 'super_admin'
-      ? '/management/users'
-      : '/security'
-
-  await router.push(target)
+  await router.push(getDefaultAuthenticatedPath(user))
 }
 
 async function onSubmit(event: FormSubmitEvent<typeof form>) {
@@ -138,7 +136,7 @@ async function onSubmit(event: FormSubmitEvent<typeof form>) {
   } catch (error: any) {
     toast.add({
       title: 'Login failed',
-      description: error?.data?.statusMessage || 'Unable to sign in with username and password.',
+      description: getErrorMessage(error, 'Unable to sign in with username and password.'),
       color: 'error',
       icon: 'i-lucide-circle-alert'
     })
@@ -184,7 +182,7 @@ async function loginWithPasskey() {
   } catch (error: any) {
     toast.add({
       title: 'Passkey login failed',
-      description: error?.data?.statusMessage || error?.message || 'Unable to complete passkey login.',
+      description: getErrorMessage(error, 'Unable to complete passkey login.'),
       color: 'error',
       icon: 'i-lucide-circle-alert'
     })