feat: add Filament admin panel with migrations and design spec

- Add AdminPanelProvider mounting panel at `/admin` with `is_admin` auth guard
- Add `is_admin` boolean column to users table
- Add brent_prices and price_predictions tables with appropriate indexes
- Add comprehensive admin design spec covering resources, dashboard, navigation, and build order
- Configure default panel with amber primary color and standard middleware stack
- Add compiled Filament assets (actions.js, app.css)

routes/console.php

@@ -21,3 +21,10 @@ Schedule::command('fuel:poll --full')
     ->withoutOverlapping()
     ->onOneServer()
     ->runInBackground();
+
+// Fetch FRED prices and generate oil price prediction daily at 7am
+Schedule::command('oil:predict --fetch')
+    ->dailyAt('07:00')
+    ->withoutOverlapping()
+    ->onOneServer()
+    ->runInBackground();