feat(currency): centralise money formatting + curated currency picker

New `src/lib/utils/currency.ts` is the single source of truth for
display formatting (`formatCurrency`) and the supported-currency
catalog (`SUPPORTED_CURRENCIES`, 10 codes covering the marina market).

New shared components:
- `<CurrencyInput>` — number input with leading symbol prefix and
  decimal inputMode, raw number value out via onChange.
- `<CurrencySelect>` — Select dropdown over `SUPPORTED_CURRENCIES`
  with symbol + code + label per row, replaces the free-text 3-letter
  inputs that let reps type "EURO" or "$$$" into a 3-char ISO column.

Threaded through every money input + display:
- Forms: berth (price/currency), expense (amount/currency), invoice
  (currency Select + line-items unit-price + step-3 review totals).
- Reads: berth-card / berth-columns / invoice-card / expense-card /
  dashboard KPIs / dashboard revenue-forecast / portal-invoices page.
  Each had its own ad-hoc `Intl.NumberFormat` wrapper with slightly
  different fallbacks; collapsed onto the shared helper.

`InvoiceLineItems` gained a `currency` prop so the unit-price input
prefix and the subtotal use the parent invoice's currency rather than
hard-coded `en-US` formatting.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/dashboard/kpi-cards.tsx

@@ -6,6 +6,7 @@ import { apiFetch } from '@/lib/api/client';
 import { useUIStore } from '@/stores/ui-store';
 import { KPITile } from '@/components/ui/kpi-tile';
 import { Skeleton } from '@/components/ui/skeleton';
+import { formatCurrency } from '@/lib/utils/currency';
 import { WidgetErrorBoundary } from './widget-error-boundary';
 
 interface KpiData {
@@ -15,13 +16,7 @@ interface KpiData {
   occupancyRate: number;
 }
 
-function formatCurrency(value: number): string {
-  return new Intl.NumberFormat('en-US', {
-    style: 'currency',
-    currency: 'USD',
-    maximumFractionDigits: 0,
-  }).format(value);
-}
+const formatUsd = (value: number) => formatCurrency(value, 'USD', { maxFractionDigits: 0 });
 
 function formatPercent(value: number): string {
   return `${value.toFixed(1)}%`;
@@ -81,7 +76,7 @@ export function KpiCards() {
     },
     {
       label: 'Pipeline Value',
-      value: isError ? '-' : formatCurrency(data?.pipelineValueUsd ?? 0),
+      value: isError ? '-' : formatUsd(data?.pipelineValueUsd ?? 0),
       accent: 'success',
     },
     {