Reverse-geocode a general area label for logged searches

Each search now stores an `area_label` (district/town) reverse-geocoded from its
coarsened ~1km lat/lng bucket via postcodes.io, surfaced in the Filament Searches
admin as a sortable/searchable column plus an area filter. Geocoding is cached 30
days per bucket, queries a 2km radius so low-density buckets still match the
default 100m miss, and fails gracefully to null. Adds `searches:backfill-areas`
(scheduled hourly) to label existing rows and retry stragglers.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Services/StationSearch/StationSearchService.php

@@ -11,6 +11,7 @@ use App\Services\Forecasting\LocalSnapshotService;
 use App\Services\Forecasting\WeeklyForecastService;
 use App\Services\HaversineQuery;
 use App\Services\PlanFeatures;
+use App\Services\PostcodeService;
 use Illuminate\Database\Query\JoinClause;
 use Illuminate\Support\Carbon;
 use Illuminate\Support\Collection;
@@ -20,6 +21,7 @@ final class StationSearchService
     public function __construct(
         private readonly WeeklyForecastService $weeklyForecast,
         private readonly LocalSnapshotService $localSnapshot,
+        private readonly PostcodeService $postcodeService,
     ) {}
 
     public function search(SearchCriteria $criteria, ?User $user, ?string $ipHash): SearchResult
@@ -118,6 +120,7 @@ final class StationSearchService
         Search::create([
             'lat_bucket' => round($criteria->lat, 2),
             'lng_bucket' => round($criteria->lng, 2),
+            'area_label' => $this->postcodeService->reverseResolve($criteria->lat, $criteria->lng),
             'fuel_type' => $criteria->fuelType->value,
             'results_count' => $resultsCount,
             'lowest_pence' => $prices->min(),