refactor: add Enum labels, fix indentation, and add URL links to StatsOverviewWidget

Adds `label()` methods to TrendDirection and PredictionSource enums for cleaner display. Fixes mixed tab/space indentation in StatsOverviewWidget. Links all stats cards to their respective Filament resources (searches, stations, oil-predictions, api-logs). Documents BrentPriceChartWidget's manual registration.

app/Enums/TrendDirection.php

@@ -7,4 +7,9 @@ enum TrendDirection: string
     case Rising = 'rising';
     case Falling = 'falling';
     case Flat = 'flat';
+
+    public function label(): string
+    {
+        return ucfirst($this->value);
+    }
 }