Add WizardLayout template with 5 layout variants

- centered-form: single column ~600px for form steps (intro, auth, etc.)
- list-map: 40/60 split for provider search (card list + map)
- list-detail: 40/60 master-detail for package selection
- grid-sidebar: 25/75 filter sidebar + card grid (coffins)
- detail-toggles: 50/50 hero image + product info (venue/coffin details)

Common elements: nav slot, sticky help bar, optional back link,
optional progress stepper + running total (grid-sidebar, detail-toggles).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/templates/WizardLayout/index.ts

@@ -0,0 +1,2 @@
+export { default } from './WizardLayout';
+export * from './WizardLayout';