fix(news): Guardian sectionName 'World news' 카테고리 매핑 (셀프 리뷰)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/workers/news_collector.py

@@ -36,6 +36,7 @@ CATEGORY_MAP = {
     "환경": "Environment", "기술": "Technology",
     # 영어
     "World": "International", "International": "International",
+    "World news": "International",  # Guardian sectionName (B-2)
     "Technology": "Technology", "Tech": "Technology", "Sci-Tech": "Technology",
     "Arts": "Culture", "Culture": "Culture",
     "Climate": "Environment", "Environment": "Environment",