fix: generate user slug on creation

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/Models/User.php

@@ -165,6 +165,17 @@ class User extends Authenticatable
         return $slug;
     }
 
+    protected static function boot()
+    {
+        parent::boot();
+
+        static::creating(function ($user) {
+            if (empty($user->slug)) {
+                $user->slug = static::generateUniqueSlug($user->name);
+            }
+        });
+    }
+
     /**
      * Get the route key for the model.
      */