Add first-class hosting subdomain create/attach in Domains panel.

Customers can create label-based subdomains under primary/addon sites with a separate max_domains×5 quota, nginx/docroot/SSL provisioning, and managed DNS A records when Ladill controls the parent zone.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Models/HostingAccount.php

@@ -311,6 +311,61 @@ class HostingAccount extends Model
         return max($included, 0);
     }
 
+    /**
+     * Domain slot limit from resource limits / product. -1 means unlimited.
+     */
+    public function maxDomainsLimit(): int
+    {
+        $limit = data_get($this->resource_limits, 'max_domains');
+        if ($limit === null) {
+            $limit = $this->product?->max_domains;
+        }
+
+        if ($limit === null) {
+            return 1;
+        }
+
+        return (int) $limit;
+    }
+
+    /**
+     * Subdomain slot limit: max_domains × 5. Unlimited domains → unlimited subdomains.
+     */
+    public function maxSubdomainsLimit(): int
+    {
+        $maxDomains = $this->maxDomainsLimit();
+
+        return $maxDomains === -1 ? -1 : max(0, $maxDomains) * 5;
+    }
+
+    public function domainSitesCount(): int
+    {
+        return $this->sites()
+            ->whereIn('type', ['primary', 'addon'])
+            ->count();
+    }
+
+    public function subdomainSitesCount(): int
+    {
+        return $this->sites()
+            ->where('type', 'subdomain')
+            ->count();
+    }
+
+    public function canAddDomain(): bool
+    {
+        $limit = $this->maxDomainsLimit();
+
+        return $limit === -1 || $this->domainSitesCount() < $limit;
+    }
+
+    public function canAddSubdomain(): bool
+    {
+        $limit = $this->maxSubdomainsLimit();
+
+        return $limit === -1 || $this->subdomainSitesCount() < $limit;
+    }
+
     public function paidMailboxCount(): int
     {
         if (! static::tracksLocalMailboxes()) {