feat: add database backup download via mysqldump (admin-only)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,29 @@
+FROM php:8.3-cli-bookworm
+
+WORKDIR /var/www/html
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        curl \
+        default-mysql-client \
+        git \
+        libicu-dev \
+        libzip-dev \
+        unzip \
+    && docker-php-ext-install \
+        intl \
+        pdo_mysql \
+        zip \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
+
+COPY docker/app/php.ini /usr/local/etc/php/conf.d/99-webgis.ini
+COPY docker/app/entrypoint.sh /usr/local/bin/webgis-entrypoint
+
+RUN chmod +x /usr/local/bin/webgis-entrypoint
+
+ENTRYPOINT ["webgis-entrypoint"]
+CMD ["php", "artisan", "serve", "--host=0.0.0.0", "--port=8000"]