feat: task file manage (#196)

1. support view task file list
2. support share file on android and iOS

ui/flutter/lib/generated/locales.g.dart

@@ -357,7 +357,7 @@ class Locales {
     'downloadDirValid': '请选择下载目录',
     'connections': '连接数',
     'maxRunning': '最大下载数',
-    'items': '@count 条',
+    'items': '@count 项',
     'subscribeTracker': '订阅 Tracker',
     'subscribeFail': '订阅失败，请检查网络或稍后重试',
     'update': '更新',