Fix health check URL to use production custom domain

Jenkins agent cannot resolve linuxpcl.azurewebsites.net due to DNS
restrictions on the build machine.

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

Jenkinsfile

@@ -83,7 +83,7 @@ pipeline {
         stage('Health Check') {
             steps {
                 powershell '''
-                    $url = "https://linuxpcl.azurewebsites.net/"
+                    $url = "https://app.powdercoatinglogix.com/"
                     $timeout = 180
                     $elapsed = 0
                     Write-Host "Polling $url for up to $timeout seconds..."