feat: implement video thumbnail generation from Cloudinary URLs

client/src/lib/media-utils.ts

@@ -0,0 +1,20 @@
+/**
+ * Derives a Cloudinary video thumbnail URL from the original video URL.
+ *
+ * Cloudinary automatically generates image frames for uploaded videos.
+ * By inserting transformation parameters into the URL, we can extract
+ * a static JPEG thumbnail without any backend change or DB migration.
+ *
+ * @param originalUrl - The Cloudinary video URL (e.g. .../video/upload/v123/file.mp4)
+ * @returns A JPEG thumbnail URL with fill-crop at 400x400
+ */
+export function getVideoThumbnailUrl(originalUrl: string): string {
+    // Only transform Cloudinary video URLs
+    if (!originalUrl.includes('/video/upload/')) {
+        return originalUrl;
+    }
+
+    return originalUrl
+        .replace('/video/upload/', '/video/upload/so_0,w_400,h_400,c_fill/')
+        .replace(/\.[^.]+$/, '.jpg');
+}