perf(litespeed): defer mariadb-server + memcached install to DEV runtime

Drops these from the build-time apt install in Dockerfile.litespeed; they
now install at entrypoint time only when environment=DEV, guarded by
'command -v mysqld' so container restarts skip the apt step.

Mirrors the cac:phpNN pattern. The mysql CLI client is already in the
litespeedtech/openlitespeed base, so wp-cli + DEV creds-bootstrap still work
without a build-time client install.

Measured (php83 / OLS 1.8.4):
  PROD image: 1.64 GB -> 1.20 GB (~440 MB savings)
  PROD first-200 boot: unchanged at ~1.5s
  DEV first boot:  ~51s (apt install cost — one-time per container)
  DEV second boot: ~6s (cache hit, same as PROD)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/entrypoint-litespeed.sh

@@ -72,8 +72,20 @@ sudo -u "$user" sh -c "echo ok > /home/$user/public_html/healthz"
 if [ "$environment" = "DEV" ]; then
   echo "Starting Dev Deployment (litespeed)"
   mkdir -p "/home/$user/_db_backups"
-  ## mariadb-server + memcached are already in the image (apt-installed
-  ## in the Dockerfile). Just start them.
+  ## mariadb-server + memcached are NOT baked into the image (saves ~500MB
+  ## on PROD pulls). Install them at runtime, but only once per container —
+  ## the command -v guard means a restart of an already-bootstrapped
+  ## container skips the apt step and DEV boot stays ~1.5s like PROD.
+  ## First-boot in DEV adds ~30-60s for the apt install; acceptable
+  ## tradeoff per the design spec.
+  if ! command -v mysqld >/dev/null 2>&1; then
+    echo "DEV first boot: installing mariadb-server + memcached..."
+    apt-get update -qq
+    DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+      mariadb-server memcached
+    apt-get clean
+    rm -rf /var/lib/apt/lists/* /var/cache/apt/archives/*
+  fi
   mkdir -p /run/mysqld && chown mysql:mysql /run/mysqld
   nohup mysqld --user=mysql &>/dev/null &
   if [ ! -f "/home/$user/mysql_creds" ]; then