CampTix: format EUR amounts via locale-aware NumberFormatter

[alexandrebuffet]

When an event uses the Euro (EUR) as its ticket currency, CampTix rendered prices as € 40.00 — the euro sign before the amount with a dot decimal separator — regardless of the site/event locale. In most Eurozone countries the convention is the symbol after the amount with a comma decimal (40,00 €).

Both defects came from the same root cause: EUR was defined with a hard-coded '€ %s' format string and (unlike GBP/en_GB or AUD/en_AU) had no locale, so it never went through NumberFormatter.

What this changes

• inc/class-camptix-currencies.php — EUR now gets a 'locale' => get_locale() so it renders through the existing NumberFormatter branch, following the site/event locale for both symbol placement and decimal/thousands separators. The '€ %s' string is kept only as a fallback for environments without the intl extension.
• camptix.php — the NumberFormatter branch now uses formatCurrency( $amount, $currency_key ) instead of format( $amount ). format() falls back to the locale's default currency, which would render a euro price with a $ on an English-language (en_US) site. formatCurrency() forces the correct ISO currency symbol.

Rendering now follows the locale for every euro-using country, including the legitimate exceptions:

Locale	Result
fr_FR, de_DE, es_ES, it_IT	40,00 €
nl_NL	€ 40,00
en_IE	€40.00
en_US	€40.00 (was $40.00)

Output for all existing locale-based currencies is unchanged — each one's locale-default currency already equals its ISO code, so format() and formatCurrency() produce byte-identical results (verified across all 18 of them against ICU 77).

Fixes #1766

Screenshots

Live example of the current (incorrect) behavior: https://bretagne.wordcamp.org/2026/billetterie/ shows € 40.00 instead of the expected 40,00 €.

How to test the changes in this Pull Request:

1. On a site whose language is a Eurozone locale (e.g. French — fr_FR), set Tickets → Setup → Currency to Euro (EUR).
2. Create a ticket with a price (e.g. 40) and view any place that renders it (ticket/registration form).
3. Confirm the price shows as 40,00 € (symbol after, comma decimal) instead of € 40.00.
4. Switch the site language to English (en_US) and confirm the price shows as €40.00 — with the euro sign, not $40.00.
5. Confirm non-euro currencies (e.g. GBP, USD, AUD) are unchanged.

Automated: tests/test-camptix-admin.php adds test_append_currency_eur_places_symbol_after_amount_for_french_locale and test_append_currency_eur_uses_euro_symbol_on_english_locale (both skip when intl is unavailable and avoid asserting exact ICU strings).

[ePascalC]

+1
This seems perfect!