Add FFmpeg updater module and GUI integration

Introduces a new FFmpeg updater module for checking and updating FFmpeg to the latest essentials build, with progress reporting and version comparison. Updates language files with new translation keys for the updater in multiple languages. Refactors Windows FFmpeg installation to use the new updater logic. Adds UpdaterTabWidget to the GUI dialogs for integration of the updater into the application's interface.

languages/zh.json

@@ -99,7 +99,8 @@
     "cookies": "使用 Cookie 登录",
     "custom_command": "自定义命令",
     "proxy": "代理",
-    "language": "语言"
+    "language": "语言",
+    "updater": "更新器"
   },
   "cookies": {
     "help_text": "选择如何提供 cookie 来登录。\n这允许下载私人视频和高级质量音频。",
@@ -466,5 +467,24 @@
     "redownload_confirm_title": "重新下载？",
     "redownload_confirm_message": "重新下载？\n\n{title}",
     "redownload_started": "已开始下载"
+  },
+  "ffmpeg_updater": {
+    "title": "FFmpeg 更新器",
+    "current_version": "当前版本：",
+    "latest_version": "最新版本：",
+    "status_up_to_date": "✓ 已是最新",
+    "status_update_available": "⚠ 有可用更新",
+    "status_not_installed": "✗ 未安装",
+    "status_checking": "🔄 正在检查更新...",
+    "status_downloading": "⬇ 正在下载 FFmpeg...",
+    "status_installing": "⚙ 正在安装 FFmpeg...",
+    "status_verifying": "✓ 正在验证完整性...",
+    "check_updates": "检查更新",
+    "update_button": "更新 FFmpeg",
+    "update_success": "FFmpeg 已成功更新到版本 {version}！",
+    "update_failed": "更新 FFmpeg 失败。请重试。",
+    "check_failed": "检查更新失败。请检查您的网络连接。",
+    "install_first": "FFmpeg 未安装。点击更新以安装。",
+    "description": "保持 FFmpeg 更新以获得最佳性能和兼容性。"
   }
 }