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>

docs/yunohost-nginx-n8n.conf

@@ -0,0 +1,49 @@
+# YunoHost nginx-Konfiguration (auf dem YunoHost-Server 192.168.179.10)
+# Ablegen als: /etc/nginx/conf.d/n8n.linix.de.conf
+# Danach: sudo nginx -t && sudo systemctl reload nginx
+#
+# Voraussetzungen auf YunoHost:
+#   1. Domain n8n.linix.de in YunoHost hinzufügen:
+#      sudo yunohost domain add n8n.linix.de
+#   2. Let's Encrypt Zertifikat ausstellen:
+#      sudo yunohost domain cert install n8n.linix.de
+#   3. Diese Datei ablegen und nginx neu laden.
+#
+# Cert-Pfad prüfen mit: ls /etc/yunohost/certs/
+
+server {
+    listen 443 ssl;
+    listen [::]:443 ssl;
+    server_name n8n.linix.de;
+
+    ssl_certificate     /etc/yunohost/certs/n8n.linix.de/crt.pem;
+    ssl_certificate_key /etc/yunohost/certs/n8n.linix.de/key.pem;
+
+    ssl_protocols       TLSv1.2 TLSv1.3;
+    ssl_prefer_server_ciphers on;
+
+    location / {
+        proxy_pass         http://192.168.179.124:8088;
+        proxy_http_version 1.1;
+
+        # WebSocket-Support
+        proxy_set_header   Upgrade    $http_upgrade;
+        proxy_set_header   Connection "upgrade";
+
+        proxy_set_header   Host              $host;
+        proxy_set_header   X-Real-IP         $remote_addr;
+        proxy_set_header   X-Forwarded-For   $proxy_add_x_forwarded_for;
+        proxy_set_header   X-Forwarded-Proto https;
+
+        proxy_read_timeout  300s;
+        proxy_send_timeout  300s;
+        client_max_body_size 50m;
+    }
+}
+
+server {
+    listen 80;
+    listen [::]:80;
+    server_name n8n.linix.de;
+    return 301 https://$host$request_uri;
+}