ci: switch from Kubernetes to Podman for local deployment

- Update Dockerfile to use fully qualified composer image name
- Replace kubectl commands with podman kube play/down in Makefile
- Change from Kubernetes Secret to ConfigMap for environment variables
- Set imagePullPolicy to Never and use localhost/ prefix for local images
- Reduce replica count to 1 for local development
- Add stop target to Makefile for easier cleanup

Dockerfile

@@ -25,7 +25,7 @@ RUN chmod +x /usr/local/bin/install-php-extensions && \
 RUN apt-get clean && rm -rf /var/lib/apt/lists/*
 
 # Get latest Composer
-COPY --from=composer:latest /usr/bin/composer /usr/bin/composer
+COPY --from=docker.io/library/composer:latest /usr/bin/composer /usr/bin/composer
 
 # Copy application files
 COPY --chown=www-data:www-data . /var/www