feat: add onboarding tutorial for new users

- Introduced a modular tutorial layer to guide new parents through the app setup process.
- Implemented a 3-step forced intro after first sign-in (PIN setup → child creation → chore creation).
- Added just-in-time contextual hints for various features as users encounter them.
- Persisted user progress on the backend with new fields in the User model.
- Created a new tutorial controller and step registry in the frontend for managing tutorial states.
- Added Help button for easy access to tutorial tips and a restart option in the user profile.
- Ensured accessibility and mobile responsiveness for the tutorial overlay.
- Included tests for backend and frontend functionalities related to the tutorial.

frontend/src/components/child/ChildEditView.vue

@@ -19,6 +19,7 @@
 import { ref, onMounted, computed, nextTick } from 'vue'
 import { useRouter } from 'vue-router'
 import EntityEditForm from '../shared/EntityEditForm.vue'
+import { maybeShow as tutorialMaybeShow } from '@/tutorial/controller'
 import '@/assets/styles.css'
 
 const router = useRouter()
@@ -55,6 +56,7 @@ const loading = ref(false)
 const error = ref<string | null>(null)
 
 onMounted(async () => {
+  if (!isEdit.value) tutorialMaybeShow('edit-child-name')
   if (isEdit.value && props.id) {
     loading.value = true
     try {