fix: remove Nexus mirror, use packagist.org directly via proxy

Dockerfile

@@ -0,0 +1,19 @@
+FROM serversideup/php:8.3-fpm-nginx
+
+ARG HTTP_PROXY
+ARG HTTPS_PROXY
+ENV HTTP_PROXY=
+ENV HTTPS_PROXY=
+
+COPY --chown=www-data:www-data . /var/www/html/
+
+ENV COMPOSER_HOME=/tmp/composer
+USER www-data
+RUN if [ -d /var/www/html/vendor ]; then \
+        COMPOSER_DISABLE_NETWORK=1 composer install --no-dev --optimize-autoloader --no-interaction 2>/dev/null || \
+        composer install --no-dev --optimize-autoloader --no-interaction; \
+    else \
+        composer install --no-dev --optimize-autoloader --no-interaction; \
+    fi
+
+EXPOSE 8080