fix(downloads): poster images not showing for downloaded content

hooks/useImageStorage.ts

@@ -1,3 +1,4 @@
+import { File, Paths } from "expo-file-system";
 import { useCallback } from "react";
 import { storage } from "@/utils/mmkv";
 
@@ -12,36 +13,32 @@ const useImageStorage = () => {
     }
   }, []);
 
+  /**
+   * expo-file-system instead of fetch+Blob+FileReader: the latter silently
+   * resolves to an empty payload under RN's New Architecture.
+   */
   const image2Base64 = useCallback(async (url?: string | null) => {
     if (!url) return null;
 
-    let blob: Blob;
+    const tmpFile = new File(
+      Paths.cache,
+      `img-${Date.now()}-${Math.random().toString(36).slice(2)}.jpg`,
+    );
     try {
-      // Fetch the data from the URL
-      const response = await fetch(url);
-      blob = await response.blob();
+      const downloaded = await File.downloadFileAsync(url, tmpFile, {
+        idempotent: true,
+      });
+      return await downloaded.base64();
     } catch (error) {
       console.warn("Error fetching image:", error);
       return null;
+    } finally {
+      try {
+        if (tmpFile.exists) tmpFile.delete();
+      } catch {
+        // best-effort cleanup
+      }
     }
-
-    // Create a FileReader instance
-    const reader = new FileReader();
-
-    // Convert blob to base64
-    return new Promise<string>((resolve, reject) => {
-      reader.onloadend = () => {
-        if (typeof reader.result === "string") {
-          // Extract the base64 string (remove the data URL prefix)
-          const base64 = reader.result.split(",")[1];
-          resolve(base64);
-        } else {
-          reject(new Error("Failed to convert image to base64"));
-        }
-      };
-      reader.onerror = reject;
-      reader.readAsDataURL(blob);
-    });
   }, []);
 
   const saveImage = useCallback(