Fix frontend Docker build dependencies

Dockerfile

@@ -1,8 +1,22 @@
+# Stage 0: PHP vendor dependencies for frontend imports
+FROM composer:2 AS vendor
+WORKDIR /app
+
+COPY composer.json composer.lock ./
+RUN composer install \
+    --no-dev \
+    --prefer-dist \
+    --no-interaction \
+    --no-progress \
+    --no-scripts \
+    --no-autoloader
+
 # Stage 1: build frontend assets
 FROM node:20-alpine AS frontend
 WORKDIR /app
 COPY package*.json ./
 RUN npm ci --no-audit
+COPY --from=vendor /app/vendor ./vendor
 COPY . .
 RUN npm run build