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>

.gitignore

@@ -0,0 +1,9 @@
+/.env
+/.env.*
+!/.env.example
+
+/backups/
+vendor/
+node_modules/
+*.log
+.DS_Store