add mp4 format hint on drop zone

Author: theJawnnybot

src/components/DropZone.css

@@ -36,6 +36,12 @@
   margin-top: 0.5rem;
 }
 
+.drop-format-hint {
+  color: #444;
+  font-size: 0.7rem;
+  margin-top: 0.75rem;
+}
+
 .drop-zone input {
   display: none;
 }

src/components/DropZone.tsx

@@ -34,6 +34,7 @@ export function DropZone({ onFile }: DropZoneProps) {
       <div className="drop-icon">🎬</div>
       <div className="drop-text">Drag & drop a video here</div>
       <div className="drop-hint">or click to browse</div>
+      <div className="drop-format-hint">MP4 recommended for best casting compatibility</div>
       <input
         ref={inputRef}
         type="file"