Add Docker Compose setup for local runs

PHP 8.3 + Apache image serving public/ on port 8080, with pdo_sqlite and
mbstring built in. The container entrypoint applies migrations as www-data
before starting Apache; the SQLite database and generated JWT signing key
persist in a named "storage" volume. `docker compose up -d` is now the
primary way to run the project without a local PHP toolchain.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,41 @@
+# syntax=docker/dockerfile:1
+
+FROM php:8.3-apache
+
+# --- PHP extensions and CLI tools ----------------------------------------------
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libsqlite3-dev \
+        libonig-dev \
+        unzip \
+        curl \
+    && docker-php-ext-install pdo_sqlite mbstring \
+    && rm -rf /var/lib/apt/lists/*
+
+# --- Composer ----------------------------------------------------------------
+COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
+
+# --- Apache: document root -> public/, allow .htaccess rewrites -------------
+RUN a2enmod rewrite
+COPY docker/apache.conf /etc/apache2/sites-available/000-default.conf
+
+WORKDIR /var/www/html
+
+# --- PHP dependencies (own layer, cached unless composer.* changes) --------
+COPY composer.json composer.lock ./
+RUN composer install --no-dev --no-interaction --no-progress --prefer-dist --no-autoloader
+
+# --- Application source ----------------------------------------------------
+COPY . .
+RUN composer dump-autoload --optimize --no-dev \
+    && mkdir -p storage \
+    && chown -R www-data:www-data storage
+
+# --- Entrypoint: migrate, then hand off to Apache ------------------------
+COPY docker/entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+CMD ["apache2-foreground"]
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s \
+    CMD curl -fsS http://localhost/api/health || exit 1