feat: Setup projet Classeo avec infrastructure Docker et architecture DDD

Configure l'environnement de développement complet avec Docker Compose,
structure DDD 4 Bounded Contexts, et pipeline CI/CD GitHub Actions.

Corrections compatibilité CI:
- Symfony 8 nécessite monolog-bundle ^4.0 (la v3.x ne supporte que jusqu'à Symfony 7)
- ESLint v9 nécessite flat config (eslint.config.js) - le format .eslintrc.cjs est obsolète

backend/Dockerfile

@@ -0,0 +1,107 @@
+# syntax=docker/dockerfile:1
+
+# =============================================================================
+# PHP 8.5 + FrankenPHP - Backend Classeo
+# =============================================================================
+
+FROM dunglas/frankenphp:1-php8.5-alpine AS base
+
+# Install system dependencies
+RUN apk add --no-cache \
+    acl \
+    fcgi \
+    file \
+    gettext \
+    git \
+    icu-dev \
+    libzip-dev \
+    postgresql-dev \
+    rabbitmq-c-dev \
+    linux-headers \
+    $PHPIZE_DEPS
+
+# Install PHP extensions (opcache is pre-installed in FrankenPHP)
+RUN docker-php-ext-install intl pdo_pgsql zip sockets
+
+# Install AMQP extension for RabbitMQ
+RUN pecl install amqp && docker-php-ext-enable amqp
+
+# Install Redis extension
+RUN pecl install redis && docker-php-ext-enable redis
+
+# Install Composer
+COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
+
+# Set working directory
+WORKDIR /app
+
+# Configure PHP for production
+RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
+
+# Custom PHP configuration
+RUN echo "opcache.enable=1" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "opcache.memory_consumption=256" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "opcache.interned_strings_buffer=16" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "opcache.max_accelerated_files=20000" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "opcache.validate_timestamps=0" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "realpath_cache_size=4096K" >> "$PHP_INI_DIR/conf.d/opcache.ini" \
+    && echo "realpath_cache_ttl=600" >> "$PHP_INI_DIR/conf.d/opcache.ini"
+
+# =============================================================================
+# Development stage
+# =============================================================================
+FROM base AS dev
+
+# Enable opcache revalidation for dev (zz- prefix loads last alphabetically)
+RUN echo "opcache.validate_timestamps=1" >> "$PHP_INI_DIR/conf.d/zz-opcache-dev.ini"
+
+# Enable Xdebug for development
+RUN pecl install xdebug && docker-php-ext-enable xdebug
+RUN echo "xdebug.mode=develop,debug,coverage" >> "$PHP_INI_DIR/conf.d/xdebug.ini" \
+    && echo "xdebug.client_host=host.docker.internal" >> "$PHP_INI_DIR/conf.d/xdebug.ini" \
+    && echo "xdebug.start_with_request=trigger" >> "$PHP_INI_DIR/conf.d/xdebug.ini"
+
+# Caddy config for FrankenPHP
+ENV SERVER_NAME=:8000
+ENV FRANKENPHP_CONFIG="worker ./public/index.php"
+
+# Create entrypoint script for dev (installs deps if needed)
+RUN echo '#!/bin/sh' > /usr/local/bin/docker-entrypoint.sh && \
+    echo 'set -e' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo 'if [ ! -f /app/vendor/autoload.php ]; then' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo '    echo "Installing Composer dependencies..."' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo '    composer install --prefer-dist --no-progress --no-interaction' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo 'fi' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo 'mkdir -p var/cache var/log && chmod -R 777 var' >> /usr/local/bin/docker-entrypoint.sh && \
+    echo 'exec "$@"' >> /usr/local/bin/docker-entrypoint.sh && \
+    chmod +x /usr/local/bin/docker-entrypoint.sh
+
+EXPOSE 8000
+
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
+CMD ["frankenphp", "run", "--config", "/etc/caddy/Caddyfile"]
+
+# =============================================================================
+# Production stage
+# =============================================================================
+FROM base AS prod
+
+ENV APP_ENV=prod
+ENV SERVER_NAME=:8000
+ENV FRANKENPHP_CONFIG="worker ./public/index.php"
+
+# Copy application files
+COPY . /app
+
+# Install dependencies (prod only, optimized)
+RUN composer install --no-dev --prefer-dist --no-progress --no-interaction --optimize-autoloader
+
+# Warmup cache
+RUN php bin/console cache:warmup
+
+# Ensure var directory exists with proper permissions
+RUN mkdir -p var/cache var/log && chmod -R 755 var
+
+EXPOSE 8000
+
+CMD ["frankenphp", "run", "--config", "/etc/caddy/Caddyfile"]