feat: support post-task script hooks (#1265)

ui/flutter/lib/i18n/langs/en_us.dart

@@ -80,6 +80,10 @@ const enUS = {
     'webhookTest': 'Test',
     'webhookTestSuccess': 'Webhook test successful',
     'webhookTestFail': 'Webhook test failed',
+    'script': 'Script',
+    'scriptEnable': 'Enable Script',
+    'scriptDesc': 'Execute custom scripts when downloads complete successfully',
+    'scriptPathHint': 'Enter script file path (e.g., /path/to/script.sh)',
     'urlInvalid': 'Please enter a valid HTTP or HTTPS URL',
     'required': 'This field is required',
     'show': 'Show',

ui/flutter/lib/i18n/langs/zh_cn.dart

@@ -78,6 +78,10 @@ const zhCN = {
     'webhookTest': '测试',
     'webhookTestSuccess': 'Webhook 测试成功',
     'webhookTestFail': 'Webhook 测试失败',
+    'script': '脚本执行',
+    'scriptEnable': '启用脚本',
+    'scriptDesc': '在下载成功完成时执行自定义脚本',
+    'scriptPathHint': '请输入脚本文件路径（例如：/path/to/script.sh）',
     'urlInvalid': '请输入有效的 HTTP 或 HTTPS 链接',
     'required': '此项为必填项',
     'show': '显示',