feat(knowledge): add KnowledgeResource with plugin hooks

- Add KnowledgeResource with user.knowledge.resource hook
- Unify processKnowledgeContent for both single and list items
- Remove isListItem parameter for cleaner architecture

app/Http/Resources/KnowledgeResource.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Http\Resources;
+
+use Illuminate\Http\Request;
+use Illuminate\Http\Resources\Json\JsonResource;
+use App\Services\Plugin\HookManager;
+
+class KnowledgeResource extends JsonResource
+{
+  /**
+   * Transform the resource into an array.
+   *
+   * @return array<string, mixed>
+   */
+  public function toArray(Request $request): array
+  {
+    $data = [
+      'id' => $this['id'],
+      'category' => $this['category'],
+      'title' => $this['title'],
+      'body' => $this->when(isset($this['body']), $this['body']),
+      'updated_at' => $this['updated_at'],
+    ];
+
+    return HookManager::filter('user.knowledge.resource', $data, $request, $this);
+  }
+}