feat: 1:1 문의 댓글 API 개선

- BoardComment 모델에 replies() 관계 추가 (children 별칭)
- PostService 댓글 CRUD에 user eager loading 추가
  - getComments(): with(['user', 'replies.user'])
  - createComment(): $comment->load('user')
  - updateComment(): $comment->fresh('user')
- 댓글 작성자 이름 정상 표시

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/Models/Boards/BoardComment.php

@@ -38,4 +38,12 @@ public function children()
     {
         return $this->hasMany(BoardComment::class, 'parent_id')->where('status', 'active');
     }
+
+    /**
+     * Alias for children() - used by PostService eager loading
+     */
+    public function replies()
+    {
+        return $this->children();
+    }
 }