feat: Restructure to subdirectories with compose.yml

Each stack now has its own directory with standard compose.yml:
- stacks/gotify/compose.yml
- stacks/prometheus/compose.yml
- stacks/grafana/compose.yml
- stacks/vaultwarden/compose.yml
- stacks/node-exporter/compose.yml

Benefits:
- Cleaner structure
- Easier to maintain
- Works with Komodo manual stack creation
- README.md for each stack with deployment info

Usage in Komodo:
1. Stacks → Add Stack
2. Source: Git Repo (nocci/komodo-stacks)
3. Path: stacks/<stack-name>/ (the folder!)
4. Deploy to server

stacks/node-exporter/README.md

@@ -0,0 +1,15 @@
+# Node Exporter
+
+📈 System-Metriken für Prometheus
+
+## Deploy in Komodo
+
+**Pfad:** `stacks/node-exporter/`
+
+## Ports
+
+- `9100` - Metrics Endpoint
+
+## Notes
+
+Keine Secrets erforderlich. Auf jedem Server installieren der überwacht werden soll.