Install intl in vendor stage

Dockerfile

@@ -1,6 +1,12 @@
 # syntax=docker/dockerfile:1.7
 
 FROM composer:2 AS vendor
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends libicu-dev \
+    && docker-php-ext-install intl \
+    && rm -rf /var/lib/apt/lists/*
+
 WORKDIR /app
 COPY composer.json composer.lock ./
 RUN --mount=type=cache,target=/tmp/composer-cache \