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/shared/currency-select.tsx

@@ -0,0 +1,48 @@
+'use client';
+
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { SUPPORTED_CURRENCIES } from '@/lib/utils/currency';
+
+interface CurrencySelectProps {
+  value: string | undefined;
+  onValueChange: (value: string) => void;
+  disabled?: boolean;
+  id?: string;
+  className?: string;
+}
+
+/**
+ * Select dropdown over the curated `SUPPORTED_CURRENCIES` list. Replaces
+ * the free-text `<Input maxLength={3}>` price-currency spots so reps
+ * can't typo "EURO" or "$$$" into a 3-letter ISO column.
+ */
+export function CurrencySelect({
+  value,
+  onValueChange,
+  disabled,
+  id,
+  className,
+}: CurrencySelectProps) {
+  return (
+    <Select value={value} onValueChange={onValueChange} disabled={disabled}>
+      <SelectTrigger id={id} className={className}>
+        <SelectValue placeholder="Select currency" />
+      </SelectTrigger>
+      <SelectContent>
+        {SUPPORTED_CURRENCIES.map((c) => (
+          <SelectItem key={c.code} value={c.code}>
+            <span className="tabular-nums mr-2">{c.symbol}</span>
+            <span className="font-medium">{c.code}</span>
+            <span className="text-muted-foreground ml-2 text-xs">{c.label}</span>
+          </SelectItem>
+        ))}
+      </SelectContent>
+    </Select>
+  );
+}