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/tune-mpm.sh

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+# Hot-adjust Apache MPM Event settings and graceful reload.
+# Usage: tune-mpm.sh [--max-workers N] [--server-limit N] [--start-servers N]
+#                     [--min-spare-threads N] [--max-spare-threads N]
+#                     [--max-connections-per-child N]
+
+set -euo pipefail
+
+# Read current values from the config as defaults
+CONFIG_FILE="/etc/httpd/conf.d/mpm-tuning.conf"
+
+if [ ! -f "$CONFIG_FILE" ]; then
+  echo "Error: $CONFIG_FILE not found. Run detect-memory.sh first."
+  exit 1
+fi
+
+# Parse current values from config
+current_start=$(grep -oP 'StartServers\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "1")
+current_min_spare=$(grep -oP 'MinSpareThreads\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "5")
+current_max_spare=$(grep -oP 'MaxSpareThreads\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "15")
+current_max_workers=$(grep -oP 'MaxRequestWorkers\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "50")
+current_server_limit=$(grep -oP 'ServerLimit\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "2")
+current_max_conn=$(grep -oP 'MaxConnectionsPerChild\s+\K\d+' "$CONFIG_FILE" 2>/dev/null || echo "3000")
+
+# Parse arguments
+START_SERVERS=$current_start
+MIN_SPARE_THREADS=$current_min_spare
+MAX_SPARE_THREADS=$current_max_spare
+MAX_REQUEST_WORKERS=$current_max_workers
+SERVER_LIMIT=$current_server_limit
+MAX_CONNECTIONS_PER_CHILD=$current_max_conn
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --max-workers) MAX_REQUEST_WORKERS="$2"; shift 2 ;;
+    --server-limit) SERVER_LIMIT="$2"; shift 2 ;;
+    --start-servers) START_SERVERS="$2"; shift 2 ;;
+    --min-spare-threads) MIN_SPARE_THREADS="$2"; shift 2 ;;
+    --max-spare-threads) MAX_SPARE_THREADS="$2"; shift 2 ;;
+    --max-connections-per-child) MAX_CONNECTIONS_PER_CHILD="$2"; shift 2 ;;
+    --help|-h)
+      echo "Usage: $0 [--max-workers N] [--server-limit N] [--start-servers N]"
+      echo "          [--min-spare-threads N] [--max-spare-threads N]"
+      echo "          [--max-connections-per-child N]"
+      echo ""
+      echo "Current values:"
+      echo "  StartServers:           $current_start"
+      echo "  MinSpareThreads:        $current_min_spare"
+      echo "  MaxSpareThreads:        $current_max_spare"
+      echo "  MaxRequestWorkers:      $current_max_workers"
+      echo "  ServerLimit:            $current_server_limit"
+      echo "  MaxConnectionsPerChild: $current_max_conn"
+      exit 0
+      ;;
+    *) echo "Unknown option: $1"; exit 1 ;;
+  esac
+done
+
+# Write updated config
+cat <<EOF > "$CONFIG_FILE"
+<IfModule mpm_event_module>
+    StartServers            ${START_SERVERS}
+    MinSpareThreads         ${MIN_SPARE_THREADS}
+    MaxSpareThreads         ${MAX_SPARE_THREADS}
+    ThreadLimit             64
+    ThreadsPerChild         25
+    MaxRequestWorkers       ${MAX_REQUEST_WORKERS}
+    ServerLimit             ${SERVER_LIMIT}
+    MaxConnectionsPerChild  ${MAX_CONNECTIONS_PER_CHILD}
+</IfModule>
+EOF
+
+echo "MPM config updated:"
+echo "  StartServers=$START_SERVERS ServerLimit=$SERVER_LIMIT MaxRequestWorkers=$MAX_REQUEST_WORKERS"
+echo "  MinSpareThreads=$MIN_SPARE_THREADS MaxSpareThreads=$MAX_SPARE_THREADS MaxConnectionsPerChild=$MAX_CONNECTIONS_PER_CHILD"
+
+# Graceful reload
+/usr/sbin/httpd -k graceful
+echo "Apache graceful reload triggered."