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/grafana/stack.toml

@@ -1,3 +1,25 @@
+[stack]
 name = "Grafana"
 description = "Grafana Dashboards & Visualisierung"
 version = "1.0.0"
+category = "monitoring"
+author = "nocci"
+
+[compose]
+file = "compose.yml"
+
+[variables.secrets]
+grafana-admin-user = "Admin Username"
+grafana-admin-pass = "Admin Password"
+
+[ports]
+grafana = "3000"
+
+[volumes]
+grafana_data = "/var/lib/grafana"
+
+[healthcheck]
+endpoint = "http://localhost:3000/api/health"
+interval = "30s"
+timeout = "10s"
+retries = 3