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/import-credentials.sh

@@ -0,0 +1,24 @@
+#!/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"
+
+if [ -z "${1:-}" ]; then
+  echo "Verwendung: $0 <credentials.json>"
+  echo "WARNUNG: Credentials-Exporte sind unverschlüsselt. Datei nach Import löschen!"
+  exit 1
+fi
+
+SOURCE="$1"
+DEST="$ROOT/imports/credentials/$(basename "$SOURCE")"
+cp "$SOURCE" "$DEST"
+
+echo "[import-credentials] Importiere: $(basename "$SOURCE")"
+echo "[import-credentials] WARNUNG: Diese Datei enthält unverschlüsselte Credentials!"
+docker compose -f "$COMPOSE" exec n8n \
+  n8n import:credentials --input="/imports/credentials/$(basename "$SOURCE")"
+
+echo "[import-credentials] Fertig."
+echo "[import-credentials] Empfehlung: Quelldatei jetzt löschen: rm '$SOURCE'"