♻️ Refactored the upload files according to new backend tasks

lib/models/upload_task.dart

@@ -0,0 +1,54 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:island/models/file.dart';
+
+part 'upload_task.freezed.dart';
+part 'upload_task.g.dart';
+
+enum UploadTaskStatus {
+  pending,
+  inProgress,
+  paused,
+  completed,
+  failed,
+  expired,
+  cancelled,
+}
+
+@freezed
+sealed class UploadTask with _$UploadTask {
+  const UploadTask._();
+
+  const factory UploadTask({
+    required String id,
+    required String taskId,
+    required String fileName,
+    required String contentType,
+    required int fileSize,
+    required int uploadedBytes,
+    required int totalChunks,
+    required int uploadedChunks,
+    required UploadTaskStatus status,
+    required DateTime createdAt,
+    required DateTime updatedAt,
+    String? errorMessage,
+    SnCloudFile? result,
+    String? poolId,
+    String? bundleId,
+    String? encryptPassword,
+    String? expiredAt,
+  }) = _UploadTask;
+
+  factory UploadTask.fromJson(Map<String, dynamic> json) =>
+      _$UploadTaskFromJson(json);
+
+  double get progress => totalChunks > 0 ? uploadedChunks / totalChunks : 0.0;
+
+  Duration get estimatedTimeRemaining {
+    if (uploadedBytes == 0 || fileSize == 0) return Duration.zero;
+    final remainingBytes = fileSize - uploadedBytes;
+    final uploadRate =
+        uploadedBytes / createdAt.difference(DateTime.now()).inSeconds.abs();
+    if (uploadRate == 0) return Duration.zero;
+    return Duration(seconds: (remainingBytes / uploadRate).round());
+  }
+}