feat: summarize 전용 stage — 뉴스 AI 요약 (classify 없이)

- summarize_worker: 요약만 생성 (분류 안 함)
- queue_consumer: summarize stage 추가 (batch 3)
- news_collector: summarize + embed 큐 등록
- process_stage enum에 'summarize' 추가

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/workers/queue_consumer.py

@@ -11,7 +11,7 @@ from models.queue import ProcessingQueue
 logger = setup_logger("queue_consumer")
 
 # stage별 배치 크기
-BATCH_SIZE = {"extract": 5, "classify": 3, "embed": 1, "preview": 2}
+BATCH_SIZE = {"extract": 5, "classify": 3, "summarize": 3, "embed": 1, "preview": 2}
 STALE_THRESHOLD_MINUTES = 10
 
 
@@ -65,10 +65,12 @@ async def consume_queue():
     from workers.embed_worker import process as embed_process
     from workers.extract_worker import process as extract_process
     from workers.preview_worker import process as preview_process
+    from workers.summarize_worker import process as summarize_process
 
     workers = {
         "extract": extract_process,
         "classify": classify_process,
+        "summarize": summarize_process,
         "embed": embed_process,
         "preview": preview_process,
     }