docs: add docker image cleanup update helper

scripts/docker-compose-update.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+IMAGE="${MEDIASTATION_IMAGE:-ghcr.io/shukebta/mediastation-go}"
+SERVICE="${MEDIASTATION_SERVICE:-mediastation-go}"
+CONTAINER="${MEDIASTATION_CONTAINER:-mediastation-go}"
+PRUNE_DANGLING="${PRUNE_DANGLING:-1}"
+PRUNE_ALL_UNUSED="${PRUNE_ALL_UNUSED:-0}"
+
+if docker compose version >/dev/null 2>&1; then
+  COMPOSE=(docker compose)
+elif command -v docker-compose >/dev/null 2>&1; then
+  COMPOSE=(docker-compose)
+else
+  echo "docker compose / docker-compose not found" >&2
+  exit 1
+fi
+
+echo "==> Pulling latest configured image"
+"${COMPOSE[@]}" pull "$SERVICE"
+
+echo "==> Recreating service"
+"${COMPOSE[@]}" up -d "$SERVICE"
+
+running_image_id="$(docker inspect -f '{{.Image}}' "$CONTAINER" 2>/dev/null || true)"
+if [[ -z "$running_image_id" ]]; then
+  echo "WARN: container '$CONTAINER' not found, skip project image cleanup" >&2
+else
+  echo "==> Removing old unused $IMAGE images"
+  while IFS= read -r image_id; do
+    [[ -z "$image_id" || "$image_id" == "$running_image_id" ]] && continue
+    docker rmi "$image_id" >/dev/null 2>&1 || true
+  done < <(docker image ls "$IMAGE" --format '{{.ID}}' | sort -u)
+fi
+
+if [[ "$PRUNE_DANGLING" == "1" ]]; then
+  echo "==> Pruning dangling image layers"
+  docker image prune -f >/dev/null
+fi
+
+if [[ "$PRUNE_ALL_UNUSED" == "1" ]]; then
+  echo "==> Pruning all unused images"
+  docker image prune -a -f >/dev/null
+fi
+
+echo "Done. Current image:"
+docker image ls "$IMAGE" --format '  {{.Repository}}:{{.Tag}}  {{.ID}}  {{.Size}}' | head -n 20