feat: Add banner toggle and soldout tracking to Cars page

- Add is_banner, soldout fields to Car model
- Add banner toggle API (POST /hero-banners/admin/toggle/{car_id})
- Add soldout APIs (POST/DELETE /cars/{car_id}/soldout)
- Add nightly soldout checker in agent (runs at 3:00 AM)
- Update Local Cars UI with banner checkbox and status column
- Remove hero-banners admin page (functionality moved to Cars page)
- Banner cars sorted to top with purple background
- Soldout cars displayed with gray overlay

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

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

backend/app/api/hero_banners.py

@@ -7,6 +7,7 @@ import aiofiles
 
 from ..database import get_db
 from ..models.hero_banner import HeroBanner, HeroBannerSettings
+from ..models.car import Car
 from ..schemas.hero_banner import (
     HeroBannerCreate, HeroBannerUpdate, HeroBannerResponse,
     HeroBannerListResponse, HeroBannerLocalizedResponse,
@@ -264,3 +265,97 @@ async def upload_banner_image(
         "image_url": image_url,
         "filename": filename,
     }
+
+
+# ==================== Banner Toggle & Ordering ====================
+
+@router.post("/admin/toggle/{car_id}")
+def toggle_banner(
+    car_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_admin_user)
+):
+    """차량의 배너 상태 토글 (Admin)
+
+    - is_banner=False → True: HeroBanner 생성
+    - is_banner=True → False: HeroBanner 삭제
+    """
+    car = db.query(Car).filter(Car.id == car_id).first()
+    if not car:
+        raise HTTPException(status_code=404, detail="Car not found")
+
+    if car.is_banner:
+        # 배너에서 제거
+        banner = db.query(HeroBanner).filter(HeroBanner.car_id == car_id).first()
+        if banner:
+            db.delete(banner)
+        car.is_banner = False
+        db.commit()
+        return {"car_id": car_id, "is_banner": False, "message": "Removed from banner"}
+    else:
+        # 배너에 추가
+        # 현재 최대 display_order 찾기
+        max_order = db.query(HeroBanner).count()
+
+        # 차량 이미지 URL
+        image_url = f"/uploads/cars/{car_id}/image_0.jpg"
+
+        # 배너 생성
+        banner = HeroBanner(
+            title_ko=car.car_name or "",
+            title_en=car.car_name or "",  # 프론트엔드에서 번역
+            title_mn=car.car_name or "",
+            title_ru=car.car_name or "",
+            subtitle_ko=f"{car.year or ''}년식 | {car.mileage:,}km" if car.mileage else f"{car.year or ''}년식",
+            subtitle_en=f"{car.year or ''} | {car.mileage:,}km" if car.mileage else f"{car.year or ''}",
+            subtitle_mn=f"{car.year or ''} | {car.mileage:,}km" if car.mileage else f"{car.year or ''}",
+            subtitle_ru=f"{car.year or ''} | {car.mileage:,}km" if car.mileage else f"{car.year or ''}",
+            image_url=image_url,
+            link_url=f"/cars/{car_id}",
+            car_id=car_id,
+            display_order=max_order,
+            is_active=True,
+        )
+        db.add(banner)
+        car.is_banner = True
+        db.commit()
+        db.refresh(banner)
+        return {"car_id": car_id, "is_banner": True, "banner_id": banner.id, "message": "Added to banner"}
+
+
+@router.put("/admin/reorder")
+def reorder_banners(
+    car_ids: List[int],
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_admin_user)
+):
+    """배너 순서 재정렬 (Admin)
+
+    car_ids: 배너 차량 ID 목록 (원하는 순서대로)
+    """
+    for order, car_id in enumerate(car_ids):
+        banner = db.query(HeroBanner).filter(HeroBanner.car_id == car_id).first()
+        if banner:
+            banner.display_order = order
+
+    db.commit()
+    return {"message": "Banner order updated", "count": len(car_ids)}
+
+
+@router.get("/admin/banner-cars")
+def get_banner_cars(
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_admin_user)
+):
+    """배너 등록된 차량 목록 조회 (Admin)
+
+    display_order 순으로 정렬된 차량 ID 목록 반환
+    """
+    banners = db.query(HeroBanner).filter(
+        HeroBanner.car_id.isnot(None)
+    ).order_by(HeroBanner.display_order.asc()).all()
+
+    return {
+        "car_ids": [b.car_id for b in banners],
+        "count": len(banners)
+    }