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

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

scripts/regenerate-sample-mp4.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Regenerate backend/media/sample.mp4 (SMPTE color bars, 45s, 1280x720 H.264).
+# Recovery only — runtime does not depend on ffmpeg.
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+OUT="$ROOT/backend/media/sample.mp4"
+mkdir -p "$(dirname "$OUT")"
+if ! command -v ffmpeg >/dev/null 2>&1; then
+  echo "ffmpeg not found" >&2
+  exit 1
+fi
+ffmpeg -y -f lavfi -i smptebars=size=1280x720:rate=24 \
+  -f lavfi -i "sine=frequency=1000:sample_rate=44100" \
+  -t 45 -c:v libx264 -pix_fmt yuv420p -c:a aac -shortest "$OUT"
+echo "Wrote $OUT"