feat: add StatsOverviewWidget to admin dashboard

Four-stat overview widget (users, stations, oil prediction, API errors)
with 30s polling registered on the admin panel dashboard.

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

app/Providers/Filament/AdminPanelProvider.php

@@ -2,6 +2,7 @@
 
 namespace App\Providers\Filament;
 
+use App\Filament\Widgets\StatsOverviewWidget;
 use Filament\Http\Middleware\Authenticate;
 use Filament\Http\Middleware\AuthenticateSession;
 use Filament\Http\Middleware\DisableBladeIconComponents;
@@ -39,6 +40,7 @@ class AdminPanelProvider extends PanelProvider
             ->discoverWidgets(in: app_path('Filament/Widgets'), for: 'App\Filament\Widgets')
             ->widgets([
                 AccountWidget::class,
+                StatsOverviewWidget::class,
             ])
             ->middleware([
                 EncryptCookies::class,