feat(clerk): add clerk-facing Cheque Book screen and shell nav wiring

Adds a customer-account-scoped Cheque Book view under Clerk > Account
Facilities (list + leaf detail, with stop-payment/report-lost/mark-used/
return actions), reachable via a new hover dropdown on the Account
Facilities nav item. Also refreshes the Account Facilities page layout,
and carries over a few chequebook service/detail-dialog fixes from the
back-office module (used-leaf display, leaf-lookup dialog polish).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/chequebook/chequebook.service.ts

@@ -166,6 +166,11 @@ export class ChequeBookService {
     return this.http.post(`/chequebooks/${bookId}`, payload, { params: new HttpParams().set('command', 'markused') });
   }
 
+  /** Flag leaves as returned/dishonoured (insufficient funds, signature mismatch, etc.) — terminal, like reportlost. */
+  returnBook(bookId: string | number, payload: any): Observable<any> {
+    return this.http.post(`/chequebooks/${bookId}`, payload, { params: new HttpParams().set('command', 'return') });
+  }
+
   // ----- Pending requests (bespoke maker-checker for series/stock/book creation) -----
 
   /**