fix: model audit cleanups (primaryKey, fuel_type cast, cadence cache)

- StationPriceCurrent: $primaryKey was null; set to 'station_id' + keyType
  string so Eloquent has a sensible default for save() / find() paths.
- UserNotificationPreference: add FuelType enum cast on fuel_type so it
  hydrates as an enum like every other price model.
- Plan::resolveCadenceForUser: cache for 1h under the same plans tag as
  resolveForUser; HandleStripeWebhook busts both keys on subscription
  events.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Listeners/HandleStripeWebhook.php

@@ -129,6 +129,8 @@ final class HandleStripeWebhook
 
     private function bustPlanCache(User $user): void
     {
-        Cache::tags(['plans'])->forget("plan_for_user_{$user->id}");
+        $tag = Cache::tags(['plans']);
+        $tag->forget("plan_for_user_{$user->id}");
+        $tag->forget("plan_cadence_for_user_{$user->id}");
     }
 }

app/Models/Plan.php

@@ -77,6 +77,12 @@ class Plan extends Model
      */
     public static function resolveCadenceForUser(User $user): ?string
     {
+        $cache = Cache::supportsTags() ? Cache::tags(['plans']) : Cache::store();
+
+        return $cache->remember(
+            "plan_cadence_for_user_{$user->id}",
+            3600,
+            function () use ($user): ?string {
                 if (! method_exists($user, 'subscriptions')) {
                     return null;
                 }
@@ -105,6 +111,8 @@ class Plan extends Model
 
                 return null;
             }
+        );
+    }
 
     protected static function booted(): void
     {

app/Models/StationPriceCurrent.php

@@ -19,7 +19,9 @@ class StationPriceCurrent extends Model
 
     public $timestamps = false;
 
-    protected $primaryKey = null;
+    protected $primaryKey = 'station_id';
+
+    protected $keyType = 'string';
 
     public $incrementing = false;
 

app/Models/UserNotificationPreference.php

@@ -2,6 +2,7 @@
 
 namespace App\Models;
 
+use App\Enums\FuelType;
 use Database\Factories\UserNotificationPreferenceFactory;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
@@ -44,6 +45,7 @@ class UserNotificationPreference extends Model
     {
         return [
             'enabled' => 'boolean',
+            'fuel_type' => FuelType::class,
         ];
     }
 }