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>

frontend/src/lib/api.ts

@@ -70,6 +70,22 @@ export const carsApi = {
     const { data } = await api.get('/cars/models/', { params });
     return data;
   },
+
+  // Soldout APIs
+  markSoldout: async (carId: number): Promise<{ car_id: number; soldout: boolean; message: string }> => {
+    const { data } = await api.post(`/cars/${carId}/soldout`);
+    return data;
+  },
+
+  markAvailable: async (carId: number): Promise<{ car_id: number; soldout: boolean; message: string }> => {
+    const { data } = await api.delete(`/cars/${carId}/soldout`);
+    return data;
+  },
+
+  getSoldoutStats: async (): Promise<{ total_active: number; soldout: number; available: number; soldout_percentage: number }> => {
+    const { data } = await api.get('/cars/admin/soldout-stats');
+    return data;
+  },
 };
 
 // Auth API
@@ -187,6 +203,22 @@ export const heroBannersApi = {
     const { data } = await api.put('/hero-banners/admin/settings', settings);
     return data;
   },
+
+  // Banner Toggle & Ordering
+  adminToggleBanner: async (carId: number): Promise<{ car_id: number; is_banner: boolean; banner_id?: number; message: string }> => {
+    const { data } = await api.post(`/hero-banners/admin/toggle/${carId}`);
+    return data;
+  },
+
+  adminReorderBanners: async (carIds: number[]): Promise<{ message: string; count: number }> => {
+    const { data } = await api.put('/hero-banners/admin/reorder', carIds);
+    return data;
+  },
+
+  adminGetBannerCars: async (): Promise<{ car_ids: number[]; count: number }> => {
+    const { data } = await api.get('/hero-banners/admin/banner-cars');
+    return data;
+  },
 };
 
 // Translations API