Add translations stage to generate Symfony translations for webpack

Webpack build requires var/translations files generated by Symfony's cache warmup. Added intermediate 'translations' stage that:
- Copies composer dependencies and app files
- Generates autoloader
- Runs cache warmup to create translation files
- Assets stage now copies these translations before building

This fixes the webpack build errors about missing translation exports.

Co-authored-by: jbtronics <5410681+jbtronics@users.noreply.github.com>

Dockerfile-frankenphp

@@ -11,6 +11,28 @@ RUN composer install --no-dev --no-scripts --no-autoloader --prefer-dist --ignor
 
 # ---
 
+# Stage to generate Symfony translations needed for webpack
+FROM composer:latest AS translations
+
+WORKDIR /build
+
+# Copy composer dependencies and application files
+COPY --from=composer-deps /build/vendor ./vendor
+COPY composer.json composer.lock symfony.lock ./
+COPY bin ./bin
+COPY config ./config
+COPY public ./public
+COPY src ./src
+COPY templates ./templates
+COPY translations ./translations
+
+# Generate autoloader and dump translations
+RUN composer dump-autoload --no-dev --classmap-authoritative && \
+    php bin/console cache:clear --no-warmup && \
+    php bin/console cache:warmup
+
+# ---
+
 FROM node:22-bookworm-slim AS assets
 
 WORKDIR /build
@@ -18,6 +40,9 @@ WORKDIR /build
 # Copy vendor directory from composer stage (needed for Symfony UX packages)
 COPY --from=composer-deps /build/vendor ./vendor
 
+# Copy generated translations from Symfony
+COPY --from=translations /build/var/translations ./var/translations
+
 # Copy package files
 COPY package.json yarn.lock webpack.config.js ./
 COPY assets ./assets