Fix role assignment: sync role_id to pivot table on user create/edit

UserForm was setting role_id on the users table but not syncing to the
role_user pivot table. Permission checks use the pivot (roles() relation),
so users appeared to have the correct role in the UI but had zero
permissions in practice.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Livewire/Users/UserForm.php

@@ -290,6 +290,11 @@ public function save(): void
                     $user = User::create($data);
                 }
 
+                // Sync role to pivot table
+                if ($this->role_id) {
+                    $user->roles()->syncWithoutDetaching([$this->role_id]);
+                }
+
                 // Link person to user
                 if ($person && ! $person->user_id) {
                     $person->update(['user_id' => $user->id]);