SummaryStep: visual cart layout with arrangement details and share dialog

- Visual cart-style cards with image thumbnails for provider, venue,
  crematorium, coffin (replaces accordion text lists)
- Arrangement details section at top: arranger name, deceased name,
  service tradition, preferred dates/times
- Location pin icons on all location-based cards
- Allowance display: fully covered shows "Included in your package",
  partially covered shows price/allowance/remaining breakdown
- Share dialog: "Share this plan" button opens DialogShell with multi-email
  input, add/remove recipients, send confirmation state
- Included services as checkmark list, extras as priced list (consistent
  tick logic — only in sections with no priced items)
- Full-width CTA, deposit deferred to payment step
- Edit buttons with pencil icon in secondary colour

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

src/components/pages/SummaryStep/index.ts

@@ -1,2 +1,7 @@
 export { SummaryStep, default } from './SummaryStep';
-export type { SummaryStepProps, SummarySection, SummaryLineItem } from './SummaryStep';
+export type {
+  SummaryStepProps,
+  SummarySection,
+  SummaryLineItem,
+  ArrangementDetails,
+} from './SummaryStep';