Fix #196: one-command operator backup (pg_dump + MinIO)

Move backup from a documented procedure to `deploy/backup.sh`: dumps Postgres
(pg_dump --clean --if-exists, gzipped) and archives the MinIO /data directory
into a single timestamped bundle under backups/. Reads config from the compose
.env with the same defaults the stack uses; optional BACKUP_RETAIN_DAYS prunes
old bundles (cron-friendly). BACKUP.md documents usage + the restore procedure
(kept manual/documented rather than an untested destructive script).

Closes #196

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

deploy/backup.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+#
+# One-command backup of a Provenance deployment: the Postgres database and the
+# MinIO object store, into a single timestamped bundle under ./backups/.
+#
+#   ./backup.sh                 # write backups/provenance-backup-<UTC>.tar
+#   BACKUP_RETAIN_DAYS=30 ./backup.sh   # also prune bundles older than 30 days
+#
+# Run it from the host where `docker compose` manages the stack (i.e. this
+# deploy/ directory). Restore steps are in BACKUP.md.
+set -euo pipefail
+
+cd "$(dirname "$0")"  # the deploy/ directory (where docker-compose.yml lives)
+
+# Config comes from the compose .env (same file the stack uses); fall back to
+# the compose defaults so a vanilla stack still backs up.
+if [ -f .env ]; then set -a; . ./.env; set +a; fi
+PGUSER="${POSTGRES_USER:-provenance}"
+PGDB="${POSTGRES_DB:-provenance}"
+
+dc() { docker compose "$@"; }
+
+ts="$(date -u +%Y%m%dT%H%M%SZ)"
+work="backups/.work-$ts"
+mkdir -p "$work" backups
+
+cleanup() { rm -rf "$work"; }
+trap cleanup EXIT
+
+echo "→ Dumping Postgres database '$PGDB'…"
+dc exec -T postgres pg_dump -U "$PGUSER" -d "$PGDB" --no-owner --clean --if-exists \
+  | gzip > "$work/db.sql.gz"
+
+echo "→ Archiving MinIO object store…"
+# Tar MinIO's data directory straight from the container (objects + bucket
+# metadata). Restored by extracting back into the miniodata volume.
+dc exec -T minio tar czf - -C /data . > "$work/minio-data.tar.gz"
+
+cat > "$work/MANIFEST.txt" <<EOF
+Provenance backup
+created:   $ts
+database:  $PGDB  (pg_dump --clean --if-exists, gzip)
+objects:   MinIO /data (tar.gz)
+restore:   see deploy/BACKUP.md
+EOF
+
+bundle="backups/provenance-backup-$ts.tar"
+# Contents are already gzipped, so the outer archive is a plain tar.
+tar cf "$bundle" -C "$work" db.sql.gz minio-data.tar.gz MANIFEST.txt
+
+echo "✓ Backup written: $bundle ($(du -h "$bundle" | cut -f1))"
+
+if [ -n "${BACKUP_RETAIN_DAYS:-}" ]; then
+  echo "→ Pruning bundles older than ${BACKUP_RETAIN_DAYS} days…"
+  find backups -maxdepth 1 -name 'provenance-backup-*.tar' -type f \
+    -mtime "+${BACKUP_RETAIN_DAYS}" -print -delete
+fi