feat: add deployment health and backups

docs/DEPLOYMENT.md

@@ -45,6 +45,42 @@ worker images share the same Node workspace image; the web image builds the Vue
 application and serves it through Nginx with SPA fallback and internal `/api`
 proxying.
 
+## Health Checks
+
+Production Compose waits for healthy PostgreSQL, Redis, and API services before
+starting the web service. The API health endpoint is `GET /health`; the web
+container checks its `/health` response through Nginx.
+
+## Backup And Restore
+
+Create a PostgreSQL custom-format dump from the running production stack:
+
+```sh
+BACKUP_DIR=/secure/backups \
+POSTGRES_DB=inventory \
+POSTGRES_USER=inventory \
+POSTGRES_PASSWORD='use-secret-storage' \
+./scripts/backup-postgres.sh
+```
+
+Restore only during a planned maintenance window because `pg_restore` replaces
+matching database objects:
+
+```sh
+BACKUP_FILE=/secure/backups/inventory-20260909T000000Z.dump \
+POSTGRES_DB=inventory \
+POSTGRES_USER=inventory \
+POSTGRES_PASSWORD='use-secret-storage' \
+./scripts/restore-postgres.sh
+```
+
+Back up image storage and the deployment `.env` through the NAS secret/backup
+system as well. Never commit either one. Before upgrading, record the current
+image tags and database migration state. To roll back, stop the application
+services, restore the previous image tags, restore the database dump if the
+schema changed, then start the stack and verify `/health` and a read-only
+catalog request.
+
 ## Reverse proxy
 
 Responsible for: