feat: complete n8n stack setup

Docker Compose stack (n8n, PostgreSQL 16, Redis 7, 1 worker) with:
- nginx local proxy on port 8088, YunoHost TLS termination config
- helper scripts: backup/restore/import/export/update
- .env.example, README with architecture, ops commands, to-do list

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/update-n8n.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT="$(dirname "$SCRIPT_DIR")"
+COMPOSE="$ROOT/compose/docker-compose.yml"
+
+echo "[update] Starte Pre-Update-Backup..."
+bash "$SCRIPT_DIR/backup-n8n.sh"
+
+echo "[update] Neue Images ziehen..."
+docker compose -f "$COMPOSE" pull
+
+echo "[update] Stack neu starten..."
+docker compose -f "$COMPOSE" up -d
+
+echo "[update] Warte 15s auf Start..."
+sleep 15
+
+echo "[update] Stack-Status nach Update:"
+docker compose -f "$COMPOSE" ps
+
+echo "[update] Update abgeschlossen."