feat(share-products): retire the Share Reference mapping, remove dead Cashier Share Collection screen

Share Products:
- "Share Reference (Cash Vault or Suspense)" removed from the accounting step (create, edit,
  preview and the read-only view tab) -- every register now books a share transaction against the
  account the money actually reached, so no product needs a placeholder asset mapping any more.
  The field is now optional server-side, not required.

Cashier:
- Removed the Share Collection screen and its three service methods. It read
  m_share_account.cashier_collected, a column that has never existed in this schema, and no other
  screen ever called it -- it could not have produced a working entry.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/app/cashier/cashier-routing.module.ts

@@ -26,7 +26,6 @@ import { VaultPositionComponent } from './vault-position/vault-position.componen
 import { AccountRegisterComponent } from './account-register/account-register.component';
 import { ClosingCashReportComponent } from './closing-cash-report/closing-cash-report.component';
 import { ExcessTransactionReportComponent } from './excess-transaction-report/excess-transaction-report.component';
-import { ShareCollectionComponent } from './share-collection/share-collection.component';
 
 const routes: Routes = [
   Route.withShell([
@@ -345,11 +344,6 @@ const routes: Routes = [
           component: ExcessTransactionReportComponent,
           data: { title: 'Excess Transaction Report', breadcrumb: 'Excess Transaction Report' }
         },
-        {
-          path: 'share-collection',
-          component: ShareCollectionComponent,
-          data: { title: 'Share Collection', breadcrumb: 'Share Collection' }
-        },
         {
           path: 'transaction-entry',
           canActivate: [CashierOnlyGuard],