feat: add configurable Horizon dashboard admin access

Add HORIZON_ALLOWED_EMAILS env var to grant additional users access to
the Horizon dashboard. Root user (User ID 0) always retains access.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: SelimSalihovic

.env.development.example

@@ -24,6 +24,11 @@ RAY_ENABLED=false
 # Enable Laravel Telescope for debugging
 TELESCOPE_ENABLED=false
 
+# Laravel Horizon Admin Access
+# Comma-separated list of email addresses allowed to access /horizon dashboard
+# The root user (User ID 0) always has access
+# HORIZON_ALLOWED_EMAILS=admin@example.com,devops@example.com
+
 # Enable Laravel Nightwatch monitoring
 NIGHTWATCH_ENABLED=false
 NIGHTWATCH_TOKEN=

app/Providers/HorizonServiceProvider.php

@@ -55,9 +55,18 @@ protected function gate(): void
         Gate::define('viewHorizon', function ($user) {
             $root_user = User::find(0);
 
-            return in_array($user->email, [
-                $root_user->email,
-            ]);
+            // Get additional allowed emails from environment variable
+            $allowedEmails = array_filter(
+                array_map('trim', explode(',', env('HORIZON_ALLOWED_EMAILS', '')))
+            );
+
+            // Merge root user email with additional allowed emails
+            $authorizedEmails = array_merge(
+                [$root_user->email],
+                $allowedEmails
+            );
+
+            return in_array($user->email, $authorizedEmails);
         });
     }
 }