fix: fall back to Bunny Storage for cover images

components/CourseCard.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { PlayCircle, Download, FileText, CheckCircle2 } from 'lucide-react';
 import { Course, SectionVariant } from '../types';
+import { CourseCoverImage } from './CourseCoverImage';
 
 interface CourseCardProps {
   course: Course;
@@ -37,8 +38,8 @@ export const CourseCard: React.FC<CourseCardProps> = ({
         onClick={() => onClick?.(course)}
         className={`relative ${aspectRatioClass} w-full overflow-hidden rounded-[8px] bg-zinc-900 shadow-xl transition-all duration-300 ease-out group-hover:scale-[1.02] group-hover:shadow-2xl group-hover:shadow-orange-500/10 group-hover:z-10 ring-0 ring-white/0 group-hover:ring-2 group-hover:ring-orange-500/40`}
       >
-        <img
-          src={course.thumbnail}
+        <CourseCoverImage
+          source={course.thumbnail}
           alt={course.title}
           loading="lazy"
           draggable={false}