Fix missing speed on SAB cards and remove incorrect missing pieces display

public/app.js

@@ -865,8 +865,8 @@ function createDownloadCard(download) {
     progressText.textContent = download.progress + '%';
     valueDiv.appendChild(progressText);
     
-    // Missing pieces text
-    if (missingMb > 0 && totalMb > 0) {
+    // Missing pieces text (only for torrent clients like qBittorrent)
+    if (download.client && (download.client === 'qbittorrent' || download.client === 'rtorrent') && missingMb > 0 && totalMb > 0) {
       const missingText = document.createElement('span');
       missingText.className = 'missing-text';
       missingText.textContent = `(missing ${missingMb.toFixed(1)} of ${totalMb.toFixed(1)} MB)`;
@@ -878,7 +878,7 @@ function createDownloadCard(download) {
     details.appendChild(progressItem);
   }
   
-  if (download.speed) {
+  if (download.speed !== undefined && download.speed !== null) {
     const speed = createDetailItem('Speed', download.speed);
     details.appendChild(speed);
   }