feat: enhance child edit and view components with improved form handling and validation

- Added `requireDirty` prop to `EntityEditForm` for dirty state management.
- Updated `ChildEditView` to handle initial data loading and image selection more robustly.
- Refactored `ChildView` to remove unused reward dialog logic and prevent API calls in child mode.
- Improved type definitions for form fields and initial data in `ChildEditView`.
- Enhanced error handling in form submissions across components.
- Implemented cross-tab logout synchronization on password reset in the auth store.
- Added tests for login and entity edit form functionalities to ensure proper behavior.
- Introduced global fetch interceptor for handling unauthorized responses.
- Documented password reset flow and its implications on session management.

frontend/vue-app/src/components/shared/LoginButton.vue

@@ -137,6 +137,11 @@ const submit = async () => {
   }
 }
 
+function handlePinInput(event: Event) {
+  const target = event.target as HTMLInputElement
+  pin.value = target.value.replace(/\D/g, '').slice(0, 6)
+}
+
 const handleLogout = () => {
   logoutParent()
   router.push('/child')
@@ -357,6 +362,7 @@ onUnmounted(() => {
         <input
           ref="pinInput"
           v-model="pin"
+          @input="handlePinInput"
           inputmode="numeric"
           pattern="\d*"
           maxlength="6"
@@ -365,7 +371,7 @@ onUnmounted(() => {
         />
         <div class="actions modal-actions">
           <button type="button" class="btn btn-secondary" @click="close">Cancel</button>
-          <button type="submit" class="btn btn-primary">OK</button>
+          <button type="submit" class="btn btn-primary" :disabled="pin.length < 4">OK</button>
         </div>
       </form>
       <div v-if="error" class="error modal-message">{{ error }}</div>