Move model observers onto attributes and tidy provider bindings.

Register observers with ObservedBy, bind the comment spam classifier, and keep AppServiceProvider focused on application wiring.

app/Models/ArtworkReaction.php

@@ -2,15 +2,18 @@
 
 namespace App\Models;
 
+use App\Observers\ArtworkReactionObserver;
+use Illuminate\Database\Eloquent\Attributes\ObservedBy;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 
 /**
- * @property int    $id
- * @property int    $artwork_id
- * @property int    $user_id
- * @property string $reaction   ReactionType slug (e.g. thumbs_up, heart, fire…)
+ * @property int $id
+ * @property int $artwork_id
+ * @property int $user_id
+ * @property string $reaction ReactionType slug (e.g. thumbs_up, heart, fire…)
  */
+#[ObservedBy([ArtworkReactionObserver::class])]
 class ArtworkReaction extends Model
 {
     public $timestamps = false;
@@ -21,7 +24,7 @@ class ArtworkReaction extends Model
 
     protected $casts = [
         'artwork_id' => 'integer',
-        'user_id'    => 'integer',
+        'user_id' => 'integer',
         'created_at' => 'datetime',
     ];