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/Http/Controllers/Api/StationController.php

@@ -7,15 +7,30 @@ use App\Http\Requests\Api\NearbyStationsRequest;
 use App\Http\Resources\Api\StationResource;
 use App\Models\Search;
 use App\Models\Station;
+use App\Services\PostcodeService;
 use Illuminate\Database\Query\JoinClause;
 use Illuminate\Http\JsonResponse;
+use Illuminate\Validation\ValidationException;
 
 class StationController extends Controller
 {
+    public function __construct(private readonly PostcodeService $postcodeService) {}
+
     public function index(NearbyStationsRequest $request): JsonResponse
     {
-        $lat = (float) $request->input('lat');
-        $lng = (float) $request->input('lng');
+        if ($request->filled('postcode')) {
+            $location = $this->postcodeService->resolve($request->string('postcode')->toString());
+
+            if ($location === null) {
+                throw ValidationException::withMessages(['postcode' => 'Postcode not found.']);
+            }
+
+            $lat = $location->lat;
+            $lng = $location->lng;
+        } else {
+            $lat = (float) $request->input('lat');
+            $lng = (float) $request->input('lng');
+        }
         $fuelType = $request->fuelType();
         $radius = $request->radius();
         $sort = $request->sort();
@@ -23,7 +38,7 @@ class StationController extends Controller
         $all = Station::query()
             ->selectRaw(
                 'stations.*, spc.price_pence, spc.fuel_type, spc.price_effective_at,
-                (6371 * acos(MAX(-1.0, MIN(1.0,
+                (6371 * acos(GREATEST(-1.0, LEAST(1.0,
                     cos(radians(?)) * cos(radians(lat)) * cos(radians(lng) - radians(?))
                     + sin(radians(?)) * sin(radians(lat))
                 )))) AS distance_km',