chore(scripts): add compose, k3s, backup, and media helpers

Automate image load, Helm install, database backup, and sample video regeneration.

scripts/backup.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Backup Postgres + RustFS volume data for pargar.
+# Usage: ./scripts/backup.sh [output-dir]
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+OUT="${1:-$ROOT/backups/$(date -u +%Y%m%dT%H%M%SZ)}"
+mkdir -p "$OUT"
+
+echo "Backing up Postgres to $OUT/postgres.sql.gz"
+docker compose -f "$ROOT/docker-compose.yml" exec -T postgres \
+  pg_dump -U "${POSTGRES_USER:-pargar}" "${POSTGRES_DB:-pargar}" | gzip > "$OUT/postgres.sql.gz"
+
+echo "Backing up RustFS volume snapshot marker to $OUT"
+docker compose -f "$ROOT/docker-compose.yml" exec -T rustfs \
+  sh -c 'tar -C /data -czf - .' > "$OUT/rustfs-data.tar.gz" || {
+  echo "Note: if rustfs tar failed, copy volume rustfs_data manually" >&2
+}
+
+echo "Done: $OUT"
+ls -lh "$OUT"