feat(tutorial): enhance help button visibility and add dialog tests

- Introduced a mechanism to hide the help button when modal dialogs are open by adding `helpButtonHidden` state in the tutorial controller.
- Updated various components to set the help button visibility based on dialog states.
- Added tests to verify help button visibility during reward and task confirmation dialogs.
- Created new E2E tests for dialog help button functionality across different assignment views.
- Refactored existing dialog components to utilize the new help button visibility logic.
- Added unit tests for `RewardConfirmDialog` and `TaskConfirmDialog` to ensure correct titles are rendered based on task type.
- Enhanced `HelpButton` component tests to validate visibility based on tutorial state.

frontend/src/tutorial/HelpButton.vue

@@ -14,7 +14,7 @@
 <script setup lang="ts">
 import { computed } from 'vue'
 import { useRoute } from 'vue-router'
-import { activeStep, maybeShow, tutorialEnabled, tutorialProgress, clearChainProgress, modalTutorialStepId } from './controller'
+import { activeStep, maybeShow, tutorialEnabled, clearChainProgress, modalTutorialStepId, helpButtonHidden } from './controller'
 
 // Map route names to the tutorial step that should re-fire when the user taps `?`.
 // Keep this list lean — only routes that have a tutorial step actually wired.
@@ -56,6 +56,7 @@ const targetStepId = computed<string | null>(() => {
 })
 
 const visible = computed(() => {
+  if (helpButtonHidden.value) return false
   if (!tutorialEnabled.value) return false
   return targetStepId.value !== null
 })