chore: docker compose, dockerfiles, caddy snippet, readme

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BCrwHHnGCB5XH968Nxokqw

core/Dockerfile

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+FROM serversideup/php:8.4-fpm-nginx AS base
+USER www-data
+COPY --chown=www-data:www-data . /var/www/html
+RUN composer install --no-dev --optimize-autoloader

core/Dockerfile.dev

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+FROM php:8.4-cli
+RUN apt-get update && apt-get install -y --no-install-recommends libpq-dev git unzip \
+    && docker-php-ext-install pdo_pgsql pgsql \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
+WORKDIR /app
+CMD ["php", "artisan", "serve", "--host=0.0.0.0", "--port=8000"]