fix: add null/false guards, proper error handling, and VNC popup fix

- Add isset() guards before count() on ipv4/ipv6 arrays in ServerResource
  to prevent PHP 8.0+ TypeError
- Add null checks after getWhmcsService() and getCP() in 18 Module methods
  and 5 ModuleFunctions methods to prevent fatal null dereference errors
- Add null guards for $whmcsService and $cp in admin.php impersonateServerOwner
- Fix HTTP status codes throughout admin.php (404, 400, 500, 502 instead of 200)
- Guard ConfigureService methods against $this->cp === false
- Use null coalescing for customfields access in initServerBuild
- Check API response code in initServerBuild instead of always returning true
- Replace exit() with RuntimeException in Curl.php
- Change catch(Exception) to catch(Throwable) in hooks.php for PHP 8.0+
- Open VNC window before AJAX call to avoid popup blocker

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

modules/servers/VirtFusionDirect/lib/Curl.php

@@ -77,7 +77,7 @@ class Curl
     {
         if ($url === null) {
             if (!isset($this->customOptions[CURLOPT_URL]) || empty($this->customOptions[CURLOPT_URL])) {
-                exit('empty url');
+                throw new \RuntimeException('Curl: empty URL provided');
             }
         }
         $this->addOption(CURLOPT_CUSTOMREQUEST, $method);