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.service.ts

@@ -364,19 +364,6 @@ export class CashierService {
     return this.http.get<any[]>('/paymenttypes');
   }
 
-  // ── Share Collection ──
-  getShareAccountForCollection(accountId: string): Observable<any> {
-    return this.http.get(`/accounts/share/${accountId}`);
-  }
-
-  collectSharePayment(data: any): Observable<any> {
-    return this.http.post('/cashier/sharecollection', data);
-  }
-
-  getShareCollectionStatus(shareAccountId: number): Observable<any> {
-    return this.http.get(`/cashier/sharecollection/${shareAccountId}`);
-  }
-
   /** One unapplied Share Sundry receipt, found by the voucher number the member quotes. */
   getShareAdvanceByVoucher(voucherNo: string, glAccountNo: string, clientId?: number): Observable<any> {
     // The voucher travels as a query parameter, not a path segment: numbers are formatted