v1.8.0: file manager improvements

- SFTP cleanup on app close and language switch
- Windows drive selector in local panel
- Browse and Refresh buttons for local panel
- Recursive upload/download/delete of folders
- Drag-and-drop between local and remote panels
- Sudo mode toggle for privileged file operations
- New i18n keys for EN/RU/ZH

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/i18n.py

@@ -275,6 +275,15 @@ _EN = {
     "parent_dir": "Parent directory",
     "refresh_files": "Refresh",
     "items_count": "{count} items",
+    "sudo_mode": "Sudo",
+    "try_sudo_hint": "Try enabling Sudo mode",
+    "uploading_dir": "Uploading folder: {name}",
+    "downloading_dir": "Downloading folder: {name}",
+    "transfer_file_progress": "File {cur}/{total}: {name}",
+    "drop_to_upload": "Drop to upload",
+    "drop_to_download": "Drop to download",
+    "recursive_delete_confirm": "Delete folder '{name}' and all contents?",
+    "drive": "Drive",
 }
 
 _RU = {
@@ -527,6 +536,15 @@ _RU = {
     "parent_dir": "Родительская папка",
     "refresh_files": "Обновить",
     "items_count": "{count} элементов",
+    "sudo_mode": "Sudo",
+    "try_sudo_hint": "Попробуйте включить Sudo",
+    "uploading_dir": "Загрузка папки: {name}",
+    "downloading_dir": "Скачивание папки: {name}",
+    "transfer_file_progress": "Файл {cur}/{total}: {name}",
+    "drop_to_upload": "Отпустите для загрузки",
+    "drop_to_download": "Отпустите для скачивания",
+    "recursive_delete_confirm": "Удалить папку '{name}' со всем содержимым?",
+    "drive": "Диск",
 }
 
 _ZH = {
@@ -779,6 +797,15 @@ _ZH = {
     "parent_dir": "上级目录",
     "refresh_files": "刷新",
     "items_count": "{count} 个项目",
+    "sudo_mode": "Sudo",
+    "try_sudo_hint": "尝试启用Sudo模式",
+    "uploading_dir": "上传文件夹: {name}",
+    "downloading_dir": "下载文件夹: {name}",
+    "transfer_file_progress": "文件 {cur}/{total}: {name}",
+    "drop_to_upload": "释放以上传",
+    "drop_to_download": "释放以下载",
+    "recursive_delete_confirm": "删除文件夹 '{name}' 及所有内容?",
+    "drive": "驱动器",
 }
 
 _TRANSLATIONS = {