fix: implementasi FilamentUser interface agar panel bisa diakses di production

- Tambah FilamentUser interface di User model
- Tambah canAccessPanel() method
- Tambah VoteObserver: broadcast notifikasi ke semua user saat vote baru
- Tambah NotificationService::toAll()
- Fix Vote model: auto-fill created_by via booted()
- Fix CashRecordObserver: fallback created_by untuk Vote

app/Observers/CashRecordObserver.php

@@ -47,7 +47,7 @@ class CashRecordObserver
                 'related_id' => $record->id,
                 'status'     => 'open',
                 'deadline'   => now()->addDays(3),
-                'created_by' => Auth::id(),
+                'created_by' => Auth::id() ?? $record->created_by,
             ]);
 
             NotificationService::toRole('ketua',