feat(cashier): denomination overdraft validation, exchange detail fix, cash exchange in reports

- Savings/Current/FD/RD withdrawal forms: card-style overdraft warning when
  requested denomination count exceeds cashier stock; submit blocked on overdraft
- Cash History detail view: show both RECEIVED and GIVEN denomination breakdowns
  for Cash Exchange (previously only RECEIVED side was displayed)
- Closing Cash Report: add Cash Exchanges section (denomination-wise received/given/net)
- Excess Transaction Report: include cash exchanges >= threshold with Type badge
  (Exchange/Txn) and ID Proof column for RBI/AML compliance
- cashier-shared.scss: etr-badge and closing-exchange-head styles
- Cash Exchange entry: overdraft warning redesigned to cx-overdraft-card BEM layout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/cashier/cashier.service.ts

@@ -30,6 +30,9 @@ export class CashierService {
   getCashExchange(id: number): Observable<any> {
     return this.http.get(`/cashexchange/${id}`);
   }
+  reverseCashExchange(id: number, reason: string): Observable<any> {
+    return this.http.post(`/cashexchange/${id}/reverse`, { reason });
+  }
 
   // ── Tellers / Cashiers ──
   getTellers(): Observable<any[]> {