Enhanced zim file loading functionality.

* We have corrected the order of obtaining ZIM files, specifically for the DWDS application. In this application, we retrieve the ZIM file from the asset folder, and there is no ZIM file inside the obb/files directory. This adjustment addresses an issue where a temporary file was mistakenly added to the files directory, causing the application to return an invalid file. By changing this order, it does not impact previous apps, as they do not have the ZIM file in the asset folder, allowing them to skip this part and function normally.

custom/src/main/java/org/kiwix/kiwixmobile/custom/main/CustomFileValidator.kt

@@ -47,10 +47,10 @@ class CustomFileValidator @Inject constructor(private val context: Context) {
     assetFile: File? = getFileFromPlayAssetDelivery()
   ): ValidationState {
     return when {
+      assetFile != null -> HasFile(assetFile)
       obbFiles.isNotEmpty() && zimFiles().isNotEmpty() -> HasBothFiles(obbFiles[0], zimFiles[0])
       obbFiles.isNotEmpty() -> HasFile(obbFiles[0])
       zimFiles.isNotEmpty() -> HasFile(zimFiles[0])
-      assetFile != null -> HasFile(assetFile)
       else -> HasNothing
     }
   }