Starterkit v1 feature/step3 ui
- Rewrite Preview.vue with 3-state flow: save → template checklist → publish
- "Save & Create Templates" is a UI transition; actual API call happens on "Publish Homepage"
- Template checklist shows mark-as-done/undo per template with progress badge
- Preview panel always visible at top; "Refresh Preview" reloads it in place
- Fix getRequiredTemplates to also filter by selected modules, not just focus areas
Bug: T420418