feat(plugin-ecommerce): add locale-aware currency formatting and symbol positioning

[teastudiopl]

This PR introduces automatic, locale-aware currency formatting using the native Intl.NumberFormat API.

It also standardizes currency symbol positions and separators across the frontend, ensuring consistent price display for different currencies in Payload e-commerce.

Changes

1. useCurrency hook

• Added locale support in formatCurrency.
• Replaced manual string formatting with Intl.NumberFormat:

return new Intl.NumberFormat(locale, {
  style: 'currency',
  currency: code,
  minimumFractionDigits: decimals,
  maximumFractionDigits: decimals,
}).format(value / Math.pow(10, decimals))

Automatically handles:

• Decimal separators (. vs ,) depending on locale
• Currency placement (before or after the value)
• Correct number of fraction digits
• Optional locale parameter allows overriding per call (default: 'en')

2. Currency display settings

Standardized symbol placement and separator:

<div className="priceCell">
  {currency.symbolPosition === 'before' ? `<span className="currencySymbol">${currency.symbol}</span>` : ''}
  {currency.symbolPosition === 'before' && currency.symbolSeparator}
  <span className="priceValue">{convertFromBaseValue({ baseValue: cellData, currency })}</span>
  {currency.symbolPosition === 'after' && currency.symbolSeparator}
  {currency.symbolPosition === 'after' ? `<span className="currencySymbol">${currency.symbol}</span>` : ''}
</div>

Ensures correct rendering for currencies that place the symbol before (EUR, USD, GBP) or after (PLN).

3. Predefined currencies

Updated standard currency definitions:

export const EUR: Currency = { code: 'EUR', decimals: 2, label: 'Euro', symbol: '€', symbolPosition: 'before', symbolSeparator: '' }
export const USD: Currency = { code: 'USD', decimals: 2, label: 'US Dollar', symbol: '$', symbolPosition: 'before', symbolSeparator: '' }
export const GBP: Currency = { code: 'GBP', decimals: 2, label: 'British Pound', symbol: '£', symbolPosition: 'before', symbolSeparator: '' }

4. Example: currenciesConfig in Payload

import { EUR as BaseEUR, USD } from '@payloadcms/plugin-ecommerce';
import type { Currency } from '@payloadcms/plugin-ecommerce/types';

const PLN = {
  code: 'PLN',
  decimals: 2,
  label: 'Polski złoty',
  symbol: 'zł',
  symbolPosition: 'after',
  symbolSeparator: ' ',
} satisfies Currency;

export const currenciesConfig = {
  supportedCurrencies: [
    PLN,
    USD,
    BaseEUR,
  ],
  defaultCurrency: 'PLN',
};

[paulpopus]

Hey, I appreciate this PR but it seems like something got really messed up in your branch

Best way to fix it would be to copy your changes into new branch that's in sync with our latest main

[teastudiopl]

new PR: #15139