feat: 뉴스 전용 페이지 + 분류 격리 + 읽음 상태

- /news 전용 페이지: 신문사 필터, 읽지않음 필터, 시간순 리스트, 미리보기
- 뉴스 분류 격리: ai_domain='News', classify 제거, embed만 등록
- is_read: 클릭 시 자동 읽음, 전체 읽음 API
- documents 목록에서 뉴스 제외 (source_channel != 'news')
- nav에 뉴스 링크 추가
- GET /api/news/articles, POST /api/news/mark-all-read

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

app/api/news.py

@@ -98,6 +98,62 @@ async def delete_source(
     return {"message": f"소스 {source_id} 삭제됨"}
 
 
+@router.get("/articles")
+async def list_articles(
+    user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+    source: str | None = None,
+    unread_only: bool = False,
+    page: int = 1,
+    page_size: int = 30,
+):
+    """뉴스 기사 목록"""
+    from sqlalchemy import func
+    from models.document import Document
+
+    query = select(Document).where(
+        Document.source_channel == "news",
+        Document.deleted_at == None,
+    )
+    if source:
+        query = query.where(Document.ai_sub_group == source)
+    if unread_only:
+        query = query.where(Document.is_read == False)
+
+    count_q = select(func.count()).select_from(query.subquery())
+    total = (await session.execute(count_q)).scalar()
+
+    query = query.order_by(Document.is_read.asc(), Document.created_at.desc())
+    query = query.offset((page - 1) * page_size).limit(page_size)
+    result = await session.execute(query)
+    items = result.scalars().all()
+
+    from api.documents import DocumentResponse
+    return {
+        "items": [DocumentResponse.model_validate(doc) for doc in items],
+        "total": total,
+        "page": page,
+    }
+
+
+@router.post("/mark-all-read")
+async def mark_all_read(
+    user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+):
+    """전체 읽음 처리"""
+    from sqlalchemy import update
+    from models.document import Document
+
+    result = await session.execute(
+        update(Document)
+        .where(Document.source_channel == "news", Document.is_read == False)
+        .values(is_read=True)
+    )
+    await session.commit()
+    return {"marked": result.rowcount}
+
+
 @router.post("/collect")
 async def trigger_collect(
     user: Annotated[User, Depends(get_current_user)],