Add audio normalization docs and translations

Document Audio Normalization (EBU R128) in README and translated READMEs, and add corresponding localization keys and help text in ytsage language files. Updates include README.md, readme-translations (ar,de,es,fr,hi,id,it,ja,pl,pt,ru,tr,zh) and ytsage/languages JSON files to explain the feature and note that normalization requires re-encoding and forcing a specific audio format (e.g. MP3 or M4A).

ytsage/languages/zh.json

@@ -314,6 +314,8 @@
     "format_mkv": "MKV（功能丰富）",
     "audio_format_settings": "音频格式设置",
     "force_audio_format": "强制仅音频下载的音频格式",
+    "audio_normalization": "音频标准化 (EBU R128)",
+    "audio_normalization_help": "启用后，音轨将被标准化。 注意：这需要重新编码，因此必须强制使用特定的音频格式（如 MP3 或 M4A）。",
     "preferred_audio_format": "首选音频格式：",
     "force_audio_format_help": "启用后，仅音频下载将转换为您的首选格式。这仅在下载音频格式时适用。",
     "audio_format_best": "最佳（不转换）",
@@ -600,4 +602,4 @@
     "update_failed": "❌ 更新失败：{error}",
     "check_failed": "检查更新失败。请检查您的网络连接。"
   }
-}
+}