Add shared httpd + PHP-FPM-only container architecture

Separate Apache and PHP-FPM into distinct container roles to reduce
per-customer memory overhead on shared servers. Adds three new images:
- Dockerfile.fpm: PHP-FPM only (no Apache), listens on TCP port 9000
- Dockerfile.shared-httpd: Apache only (no PHP), with SSL and proxy_fcgi
- Existing Dockerfile unchanged for standalone mode

Key changes:
- detect-memory.sh: CONTAINER_ROLE env var (combined/fpm_only/httpd_only)
  controls the memory budget split
- create-php-config.sh: FPM_LISTEN env var for TCP port vs Unix socket,
  added /fpm-ping and /fpm-status health endpoints
- New entrypoints for each container role
- tune-mpm.sh for hot-adjusting Apache MPM settings
- shared-vhost-template.tpl with proxy_fcgi and SSL on port 443
- CI/CD builds all three image types in parallel

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/create-php-config.sh

@@ -2,15 +2,28 @@
 
 rm /etc/php-fpm.d/www.conf
 
+FPM_LISTEN=${FPM_LISTEN:-/run/php-fpm/www.sock}
+
+# Determine listen directive and ownership based on socket vs TCP
+if echo "$FPM_LISTEN" | grep -q '/'; then
+  # Unix socket mode
+  listen_directive="$FPM_LISTEN"
+  listen_owner_block="listen.owner = apache
+listen.group = apache"
+else
+  # TCP port mode
+  listen_directive="0.0.0.0:${FPM_LISTEN}"
+  listen_owner_block=""
+fi
+
 cat <<EOF > /etc/php-fpm.d/$user.conf
 
 [$user]
 
 user = $user
 group = $user
-listen = /run/php-fpm/www.sock
-listen.owner = apache
-listen.group = apache
+listen = ${listen_directive}
+${listen_owner_block}
 
 pm = ${PHP_FPM_PM}
 pm.max_children = ${PHP_FPM_MAX_CHILDREN}
@@ -22,7 +35,12 @@ pm.start_servers = ${PHP_FPM_START_SERVERS}
 pm.min_spare_servers = ${PHP_FPM_MIN_SPARE}
 pm.max_spare_servers = ${PHP_FPM_MAX_SPARE}
 
-slowlog = /etc/httpd/logs/error_log
+; Health check endpoints
+ping.path = /fpm-ping
+ping.response = pong
+pm.status_path = /fpm-status
+
+slowlog = /home/$user/logs/php-fpm/slowlog
 request_slowlog_timeout = 3s
 
 php_admin_value[error_log] = /home/$user/logs/php-fpm/error.log