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/(dashboard)/[portSlug]/invoices/new/page.tsx

@@ -22,8 +22,10 @@ import {
 } from '@/components/ui/select';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import { OwnerPicker } from '@/components/shared/owner-picker';
+import { CurrencySelect } from '@/components/shared/currency-select';
 import { InvoiceLineItems } from '@/components/invoices/invoice-line-items';
 import { apiFetch } from '@/lib/api/client';
+import { formatCurrency } from '@/lib/utils/currency';
 import { createInvoiceSchema, type CreateInvoiceInput } from '@/lib/validators/invoices';
 
 const PAYMENT_TERMS = [
@@ -324,11 +326,10 @@ export default function NewInvoicePage() {
 
                 <div className="space-y-1">
                   <Label>Currency</Label>
-                  <Input
-                    {...register('currency')}
-                    placeholder="USD"
-                    maxLength={3}
-                    className="uppercase w-24"
+                  <CurrencySelect
+                    value={watchedValues.currency ?? 'USD'}
+                    onValueChange={(v) => setValue('currency', v, { shouldDirty: true })}
+                    className="w-48"
                   />
                 </div>
 
@@ -352,7 +353,7 @@ export default function NewInvoicePage() {
                 <CardTitle className="text-base">Line Items</CardTitle>
               </CardHeader>
               <CardContent>
-                <InvoiceLineItems name="lineItems" />
+                <InvoiceLineItems name="lineItems" currency={watchedValues.currency ?? 'USD'} />
                 {errors.lineItems && !Array.isArray(errors.lineItems) && (
                   <p className="text-xs text-destructive mt-2">
                     {(errors.lineItems as { message?: string }).message}
@@ -415,8 +416,10 @@ export default function NewInvoicePage() {
                       <div key={i} className="flex justify-between text-sm">
                         <span>{li.description}</span>
                         <span className="tabular-nums">
-                          {(Number(li.quantity) * Number(li.unitPrice)).toFixed(2)}{' '}
-                          {watchedValues.currency}
+                          {formatCurrency(
+                            Number(li.quantity) * Number(li.unitPrice),
+                            watchedValues.currency,
+                          )}
                         </span>
                       </div>
                     ))}
@@ -427,21 +430,21 @@ export default function NewInvoicePage() {
                   <div className="flex justify-between">
                     <span className="text-muted-foreground">Subtotal</span>
                     <span className="tabular-nums">
-                      {subtotal.toFixed(2)} {watchedValues.currency}
+                      {formatCurrency(subtotal, watchedValues.currency)}
                     </span>
                   </div>
                   {isNet10 && (
                     <div className="flex justify-between text-green-600">
                       <span>Net 10 Discount (~2%)</span>
                       <span className="tabular-nums">
-                        -{discountAmount.toFixed(2)} {watchedValues.currency}
+                        -{formatCurrency(discountAmount, watchedValues.currency)}
                       </span>
                     </div>
                   )}
                   <div className="flex justify-between font-semibold border-t pt-2 mt-1">
                     <span>Total</span>
                     <span className="tabular-nums">
-                      {total.toFixed(2)} {watchedValues.currency}
+                      {formatCurrency(total, watchedValues.currency)}
                     </span>
                   </div>
                 </div>