feat: Add DNS configuration check and update subdomain management UI

extensions/Servers/Proxmox/Livewire/Subdomain.php

@@ -107,10 +107,16 @@ class Subdomain extends Component
         'walrus','warthog','weasel','whale','wolf','wolverine','wombat','woodpecker','yak','zebra',
     ];
 
+    public bool $dnsConfigured = false;
+
     public function mount(Server $server): void
     {
         parent::mount($server);
-        $this->loadServerZones();
+        $this->dnsConfigured = TechnitiumDns::isConfigured();
+
+        if ($this->dnsConfigured) {
+            $this->loadServerZones();
+        }
     }
 
     /**

extensions/Servers/Proxmox/TechnitiumDns.php

@@ -11,6 +11,15 @@ class TechnitiumDns
     private string $baseUrl;
     private string $token;
 
+    /**
+     * Check whether Technitium DNS credentials are configured.
+     */
+    public static function isConfigured(): bool
+    {
+        return !empty(config('services.technitium.url'))
+            && !empty(config('services.technitium.token'));
+    }
+
     public function __construct()
     {
         $this->baseUrl = rtrim((string) config('services.technitium.url', ''), '/');

extensions/Servers/Proxmox/views/subdomain.blade.php

@@ -4,6 +4,15 @@
         <x-ri-arrow-right-s-line class="size-3" />
         <span class="text-base/70">Subdomain</span>
     </div>
+
+    @if (!$dnsConfigured)
+        <div class="rounded-xl border border-warning/30 bg-warning/5 p-6 text-center">
+            <x-ri-error-warning-line class="size-8 mx-auto text-warning mb-3" />
+            <h3 class="text-lg font-semibold mb-1">DNS Not Configured</h3>
+            <p class="text-sm text-base/60">Subdomain management is unavailable. The administrator needs to set the <code class="text-xs bg-neutral/30 px-1.5 py-0.5 rounded">TECHNITIUM_DNS_URL</code> and <code class="text-xs bg-neutral/30 px-1.5 py-0.5 rounded">TECHNITIUM_DNS_TOKEN</code> environment variables.</p>
+        </div>
+    @else
+
     <div class="flex items-center justify-between mb-6">
         <div>
             <div class="flex items-center gap-2 min-w-0">
@@ -470,5 +479,6 @@
             </div>
         </div>
     @endif
+    @endif {{-- dnsConfigured --}}
 </x-proxmox::layout>