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>

docker-compose.staging.yml

@@ -0,0 +1,40 @@
+x-env-type: &env-type
+  WP_ENVIRONMENT_TYPE: staging
+
+services:
+  wordpress:
+    environment: *env-type
+
+  cron:
+    environment: *env-type
+
+  caddy:
+    image: caddy:2-alpine
+    restart: unless-stopped
+    depends_on:
+      - wordpress
+    ports:
+      - "80:80"
+      - "443:443"
+    environment:
+      SITE_DOMAIN: ${SITE_DOMAIN}
+      STAGING_BASIC_AUTH_USER: ${STAGING_BASIC_AUTH_USER}
+      STAGING_BASIC_AUTH_HASH: ${STAGING_BASIC_AUTH_HASH}
+    volumes:
+      - ./docker/caddy/Caddyfile.staging:/etc/caddy/Caddyfile:ro
+      - wp_core:/var/www/html:ro
+      - wp_uploads:/var/www/html/wp-content/uploads:ro
+      - wp_themes:/var/www/html/wp-content/themes:ro
+      - ./wp-content/plugins/bookstore-core:/var/www/html/wp-content/plugins/bookstore-core:ro
+      - caddy_data:/data
+      - caddy_config:/config
+
+  mailhog:
+    image: mailhog/mailhog:v1.0.1
+    restart: unless-stopped
+    ports:
+      - "8025:8025"
+
+volumes:
+  caddy_data:
+  caddy_config: