feat(loyalty): add full i18n support for all loyalty module pages

Replace hardcoded English strings across all 22 templates, 10 JS files,
and 4 locale files (en/fr/de/lb) with ~300 translation keys per language.
Uses server-side _() for Jinja2 templates and I18n.t() for JS toast
messages and dynamic Alpine.js expressions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/loyalty/static/shared/js/loyalty-program-form.js

@@ -99,7 +99,7 @@ function createProgramFormMixin() {
             if (!payload.card_name) payload.card_name = null;
             if (!payload.card_secondary_color) payload.card_secondary_color = null;
             if (!payload.logo_url) {
-                this.error = 'Logo URL is required for wallet integration.';
+                this.error = I18n.t('loyalty.toasts.logo_required');
                 return null;
             }
             if (!payload.hero_image_url) payload.hero_image_url = null;