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/User.php

@@ -13,13 +13,14 @@ use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
 use Illuminate\Support\Str;
 use Laravel\Fortify\TwoFactorAuthenticatable;
+use Laravel\Sanctum\HasApiTokens;
 
 #[Fillable(['name', 'email', 'password', 'is_admin', 'postcode'])]
 #[Hidden(['password', 'two_factor_secret', 'two_factor_recovery_codes', 'remember_token'])]
 class User extends Authenticatable implements FilamentUser
 {
     /** @use HasFactory<UserFactory> */
-    use HasFactory, Notifiable, TwoFactorAuthenticatable;
+    use HasApiTokens, HasFactory, Notifiable, TwoFactorAuthenticatable;
 
     /**
      * Get the attributes that should be cast.