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/leaf-lookup/leaf-lookup.component.scss

@@ -116,6 +116,11 @@
     background: #e0e0e0;
     color: #757575;
   }
+
+  &.returned {
+    background: #f3e8fd;
+    color: #9333ea;
+  }
 }
 
 .empty-state {