feat: Add complete stack.toml files with full metadata

Each stack.toml now includes:
- [stack] section: name, description, version, category, author
- [compose] section: file reference
- [variables] section: secrets where required
- [ports] section: internal port mappings
- [volumes] section: volume definitions
- [healthcheck] section: health check configuration

Stacks updated:
- prometheus
- grafana
- gotify
- vaultwarden
- node-exporter

stacks/node-exporter/stack.toml

@@ -1,3 +1,21 @@
+[stack]
 name = "Node Exporter"
-description = "System-Metriken"
+description = "System-Metriken für Prometheus"
 version = "1.0.0"
+category = "monitoring"
+author = "nocci"
+
+[compose]
+file = "compose.yml"
+
+[variables]
+# Keine Secrets erforderlich
+
+[ports]
+node_exporter = "9100"
+
+[healthcheck]
+endpoint = "http://localhost:9100/metrics"
+interval = "30s"
+timeout = "10s"
+retries = 3