Fix download.bin filename flickering during unrestrict

Keep existing good filename when debrid API returns "download.bin"
or opaque name. Only overwrite item.fileName if the resolved name
is actually better (not opaque, not download.bin).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "real-debrid-downloader",
-  "version": "1.4.78",
+  "version": "1.4.79",
   "description": "Real-Debrid Downloader Desktop (Electron + React + TypeScript)",
   "main": "build/main/main/main.js",
   "author": "Sucukdeluxe",

src/main/download-manager.ts

@@ -3346,7 +3346,14 @@ export class DownloadManager extends EventEmitter {
         }
         item.provider = unrestricted.provider;
         item.retries += unrestricted.retriesUsed;
-        item.fileName = sanitizeFilename(unrestricted.fileName || filenameFromUrl(item.url));
+        const resolvedName = sanitizeFilename(unrestricted.fileName || filenameFromUrl(item.url));
+        // Only overwrite fileName if the resolved name is better (not "download.bin" / opaque)
+        if (resolvedName && !looksLikeOpaqueFilename(resolvedName) && resolvedName.toLowerCase() !== "download.bin") {
+          item.fileName = resolvedName;
+        } else if (looksLikeOpaqueFilename(item.fileName)) {
+          // Current name is also opaque, use whatever we got
+          item.fileName = resolvedName;
+        }
         try {
           fs.mkdirSync(pkg.outputDir, { recursive: true });
         } catch (mkdirError) {