Week 1 infrastructure: Docker environments, deploy pipeline, bookstore-core scaffold

Docker Compose environments for dev/staging/production (MariaDB, Redis,
Caddy, Action Scheduler cron sidecar), an idempotent deploy script,
git-hook-based deploy pipeline, backup/restore scripts, and the
bookstore-core plugin stub with WooCommerce HPOS compatibility declared.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

wp-content/mu-plugins/local-mail-catcher.php

@@ -0,0 +1,22 @@
+<?php
+/**
+ * Route outgoing mail to a local catcher outside production, so no test
+ * email ever reaches a real customer (design doc §01/§08).
+ *
+ * Same code in every environment — the only thing that changes is the
+ * WP_ENVIRONMENT_TYPE define set per-environment in docker-compose.
+ */
+
+defined('ABSPATH') || exit;
+
+if (wp_get_environment_type() === 'production') {
+    return;
+}
+
+add_action('phpmailer_init', function ($phpmailer) {
+    $phpmailer->isSMTP();
+    $phpmailer->Host = getenv('MAIL_CATCHER_HOST') ?: 'mailhog';
+    $phpmailer->Port = getenv('MAIL_CATCHER_PORT') ?: 1025;
+    $phpmailer->SMTPAuth = false;
+    $phpmailer->SMTPAutoTLS = false;
+});