feat: add postcode resolution to /api/stations and Filament SearchResource

Extends NearbyStationsRequest to accept `postcode` (full or outcode) as an alternative to lat/lng. PostcodeService resolves it via postcodes.io and falls through to coordinates. Also adds SearchResource to the Filament admin panel for viewing logged search activity with fuel type filter and price/distance stats columns. Includes SQLite GREATEST/LEAST function polyfills in AppServiceProvider for test compatibility.

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

app/Models/PricePrediction.php

@@ -6,6 +6,7 @@ use App\Enums\PredictionSource;
 use App\Enums\TrendDirection;
 use Database\Factories\PricePredictionFactory;
 use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Support\Carbon;
@@ -18,6 +19,8 @@ use Illuminate\Support\Carbon;
  * @property int $confidence
  * @property string|null $reasoning
  * @property Carbon $generated_at
+ *
+ * @method static Builder<PricePrediction> bestFirst()
  */
 #[Fillable(['predicted_for', 'source', 'direction', 'confidence', 'reasoning', 'generated_at'])]
 class PricePrediction extends Model
@@ -37,4 +40,21 @@ class PricePrediction extends Model
             'generated_at' => 'datetime',
         ];
     }
+
+    /**
+     * Order by source quality: llm_with_context → llm → ewma.
+     * Use this whenever reading the "best" prediction for a given date.
+     *
+     * @param  Builder<PricePrediction>  $query
+     * @return Builder<PricePrediction>
+     */
+    public function scopeBestFirst(Builder $query): Builder
+    {
+        $priority = implode(', ', array_map(
+            fn (string $v) => "'$v'",
+            [PredictionSource::LlmWithContext->value, PredictionSource::Llm->value, PredictionSource::Ewma->value],
+        ));
+
+        return $query->orderByRaw("FIELD(source, $priority)");
+    }
 }