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/summarize_worker.py

@@ -0,0 +1,35 @@
+"""요약 전용 워커 — 뉴스 등 classify 불필요한 문서의 AI 요약만 생성"""
+
+from datetime import datetime, timezone
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from ai.client import AIClient, strip_thinking
+from core.utils import setup_logger
+from models.document import Document
+
+logger = setup_logger("summarize_worker")
+
+
+async def process(document_id: int, session: AsyncSession) -> None:
+    """문서 AI 요약 생성 (분류 없이 요약만)"""
+    doc = await session.get(Document, document_id)
+    if not doc:
+        raise ValueError(f"문서 ID {document_id}를 찾을 수 없음")
+
+    if not doc.extracted_text:
+        raise ValueError(f"문서 ID {document_id}: extracted_text가 비어있음")
+
+    if doc.ai_summary:
+        logger.info(f"[요약] document_id={document_id}: 이미 요약 있음, skip")
+        return
+
+    client = AIClient()
+    try:
+        summary = await client.summarize(doc.extracted_text[:15000])
+        doc.ai_summary = strip_thinking(summary)
+        doc.ai_model_version = "qwen3.5-35b-a3b"
+        doc.ai_processed_at = datetime.now(timezone.utc)
+        logger.info(f"[요약] document_id={document_id}: {len(doc.ai_summary)}자")
+    finally:
+        await client.close()