chore(docker): add vendor to .dockerignore, update Composer installation in Dockerfile, and clean up README instructions

Dockerfile

@@ -2,11 +2,13 @@ FROM php:8.4-fpm-bookworm AS app
 WORKDIR /var/www/html
 
 ENV COMPOSER_ALLOW_SUPERUSER=1
+ENV COMPOSER_PROCESS_TIMEOUT=600
 
 RUN apt-get update \
     && apt-get install -y --no-install-recommends \
         default-mysql-client \
         default-libmysqlclient-dev \
+        git \
         libicu-dev \
         libzip-dev \
         unzip \
@@ -25,9 +27,12 @@ COPY docker/php/php.ini /usr/local/etc/php/conf.d/99-production.ini
 COPY docker/php/opcache.ini /usr/local/etc/php/conf.d/99-opcache.ini
 
 COPY composer.json composer.lock ./
-COPY vendor ./vendor
-RUN test -f vendor/autoload.php || (echo "ERROR: vendor folder is missing. Run: composer install --no-dev" >&2 && exit 1) \
-    && composer dump-autoload --no-dev --optimize --no-scripts \
+RUN composer install \
+        --no-dev \
+        --no-autoloader \
+        --no-scripts \
+        --prefer-dist \
+        --no-interaction \
     && composer check-platform-reqs --no-dev
 
 COPY . .