feat(ui): Quick-Toggles, Config-Preview, Dashboard-Alerts, Domain-Detail-Health

Quick-Toggle-Switches (kein Modal nötig) für: Backends, Backend-Server,
DNS-Zonen, DNS-Records, Domains (active), Firewall-Rules, NAT-Rules,
Forward-Proxy ACLs, Routing-Rules.

Dashboard: Alert-Banner für komplett ausgefallene Backends (HAProxy-Stats)
und Domains im Maintenance-Mode.

Domain-Detail: HAProxy-Live-Health-Badge (15s Polling), TLS-Cert
ausstellen/erneuern direkt aus dem Detail, Routing-Rules-Panel inline.

Config-Preview (Settings): alle 4 Generatoren (haproxy, nftables, squid,
unbound) rendern via RenderToString ohne Disk-Write — GET /system/config-preview.

ActionButtons: Viewer-Rolle blendet Delete aus (RBAC-Ergänzung).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/edgeguard-api/main.go

@@ -60,7 +60,7 @@ import (
 	usersvc "git.netcell-it.de/projekte/edgeguard-native/internal/services/users"
 )
 
-var version = "1.0.78"
+var version = "1.1.72"
 
 func main() {
 	addr := os.Getenv("EDGEGUARD_API_ADDR")
@@ -267,6 +267,12 @@ func main() {
 		// /var/lib/edgeguard/node-id.
 		systemHdl.WithAudit(auditRepo, nodeID)
 		systemHdl.WithDB(pool)
+		systemHdl.WithConfigPreviewers(map[string]func(context.Context) (string, error){
+				"haproxy":  haproxy.New(pool).RenderToString,
+				"nftables": firewallrender.New(pool).RenderToString,
+				"squid":    squidrender.New(pool).RenderToString,
+				"unbound":  unboundrender.New(pool).RenderToString,
+			})
 		setupHdl.WithAudit(auditRepo, nodeID)
 		usersRepo := usersvc.New(pool)
 		authHdl.WithAudit(auditRepo, nodeID).WithUsers(usersRepo)