Move service images to root level; set CakePHP path to /var/www/cakephp

[Copilot]

Reorganizes the Docker service directories from deployment/images/ to root level, and standardizes the CakePHP installation path to /var/www/cakephp across all services.

Service directory restructure

• git mv deployment/images/mysqldb → mysqldb/
• git mv deployment/images/httpd → httpd/
• Removed empty deployment/ tree

CakePHP path: /var/www/html → /var/www/cakephp

• All php-fpm Dockerfiles (Dockerfile.{template,armhf,aarch64,x86_64}): updated ENV HTDOCS default
• All httpd Dockerfiles (httpd/Dockerfile.*): updated ENV HTDOCS default
• etc/php-fpm.d/www.conf: prefix = /var/www/cakephp (was /var/$pool/html) — aligns PHP-FPM chroot with new install path

Config/compose updates

• docker-compose.{template,armhf,aarch64,x86_64,yml}: context, HTDOCS build arg, and www: volume mount updated
• docker-bake.hcl: context paths ("mysqldb", "httpd") and HTDOCS args
• common.env: BALENA_PROJECTS array updated to ( ./httpd ./mysqldb . ./balena-storage )
• deploy.sh: mysqldb/conf.d/custom.cnf path
• kubernetes/*/: service path references updated

# Before
db:
  build:
    context: deployment/images/mysqldb
php-fpm:
  build:
    args:
      HTDOCS: /var/www/html
  volumes:
    - www:/var/www/html

# After
db:
  build:
    context: mysqldb
php-fpm:
  build:
    args:
      HTDOCS: /var/www/cakephp
  volumes:
    - www:/var/www/cakephp

Both php-fpm and httpd share the www named volume mounted at /var/www/cakephp, so Apache can serve CakePHP static assets directly while proxying PHP requests to PHP-FPM.