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/currency-exchange-detail/currency-exchange-detail.component.html

@@ -18,6 +18,10 @@
     </a>
   </header>
 
+  @if (loading) {
+    <div class="pg-empty">Loading…</div>
+  }
+
   <div class="pg-card">
     <table class="pg-table">
       <thead>