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/shared/ChildrenListView.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { ref, onMounted, onBeforeUnmount, onUnmounted, watch } from 'vue'
+import { ref, onMounted, onBeforeUnmount, onUnmounted, watch, nextTick } from 'vue'
 import { useRouter } from 'vue-router'
 import { getCachedImageUrl, revokeAllImageUrls } from '../../common/imageCache'
 import { isParentAuthenticated } from '../../stores/auth'
@@ -160,9 +160,14 @@ function maybeTriggerCreateChildTutorial() {
   if (loading.value) return
   if (!tutorialReady.value) return
   if (children.value.length === 0) {
-    tutorialMaybeShow('create-child', () => document.querySelector('.fab') as HTMLElement | null)
+    nextTick(() => {
+      tutorialMaybeShow('create-child')
+    })
   } else {
     void tutorialMark('has-created-child')
+    nextTick(() => {
+      tutorialMaybeShow('child-points')
+    })
   }
 }