Add Docker development environment

Multistage Dockerfile (WooCommerce download, wp-bootstrap npm build,
Composer deps, WordPress runtime), Compose stack with MariaDB, and
auto-setup entrypoint that installs WordPress and activates the theme
on first boot.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/entrypoint.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+#
+# Wrapper entrypoint: runs first-time WordPress setup in the background,
+# then hands off to the official WordPress entrypoint.
+#
+# Set WP_AUTO_SETUP=0 to disable automatic setup.
+#
+
+if [ "${WP_AUTO_SETUP:-1}" = "1" ]; then
+    (
+        cd /var/www/html
+        until [ -f wp-config.php ]; do sleep 2; done
+        sleep 3
+
+        if ! wp core is-installed --allow-root 2>/dev/null; then
+            setup.sh
+        fi
+    ) &
+fi
+
+exec docker-entrypoint.sh "$@"