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/app/(portal)/portal/invoices/page.tsx

@@ -5,6 +5,7 @@ import type { Metadata } from 'next';
 import { getPortalSession } from '@/lib/portal/auth';
 import { getClientInvoices } from '@/lib/services/portal.service';
 import { Badge } from '@/components/ui/badge';
+import { formatCurrency } from '@/lib/utils/currency';
 
 export const metadata: Metadata = { title: 'Invoices' };
 
@@ -16,16 +17,6 @@ const STATUS_COLORS: Record<string, 'default' | 'secondary' | 'destructive' | 'o
   cancelled: 'destructive',
 };
 
-function formatCurrency(amount: string, currency: string): string {
-  const num = parseFloat(amount);
-  if (isNaN(num)) return `${currency} ${amount}`;
-  return new Intl.NumberFormat('en-US', {
-    style: 'currency',
-    currency,
-    minimumFractionDigits: 2,
-  }).format(num);
-}
-
 export default async function PortalInvoicesPage() {
   const session = await getPortalSession();
   if (!session) redirect('/portal/login');