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/prometheus/README.md

@@ -0,0 +1,19 @@
+# Prometheus
+
+📊 Monitoring & Alerting System
+
+## Deploy in Komodo
+
+**Pfad:** `stacks/prometheus/`
+
+## Ports
+
+- `9090` - Web UI
+
+## Caddy
+
+```caddyfile
+prometheus.example.com {
+    reverse_proxy localhost:9090
+}
+```