Add generic-mode URL validation and UI

Introduce a "generic_mode" option to allow validating/downloading from non-YouTube sites and wire it through the UI, config, and validation logic. Key changes:

- Add generic_mode default to ConfigManager and persist setting from DownloadSettingsDialog (checkbox + help text).
- Extend validate_video_url to accept a generic_mode flag and allow any http/https URL with a domain when enabled; pass this flag from Analysis and Download flows.
- Update YTSageApp to load/save generic_mode, update URL placeholder and settings tooltip behavior, and refresh tooltip when settings change.
- Improve robustness in FormatTableMixin: handle None/incorrect types for format_note, abr, resolution, ext, and codec values to avoid type errors and ensure consistent display.
- Add localization entries for generic mode, placeholder, and related help text across multiple language files and update the in-app default localization strings.

These changes enable broader site support via yt-dlp while hardening UI format handling and keeping user settings persistent.

ytsage/languages/ja.json

@@ -274,6 +274,9 @@
     "browse": "参照...",
     "speed_limit": "速度制限",
     "speed_limit_placeholder": "なし",
+    "generic_mode": "汎用モード",
+    "enable_generic_mode": "汎用モードを有効化（YouTube以外のサイトをサポート）",
+    "generic_mode_help": "Dailymotion、CBC Gem、および yt-dlp が対応する他のサイトからのダウンロードを可能にします。",
     "auto_update_ytdlp": "yt-dlp自動更新",
     "enable_auto_updates": "yt-dlp自動更新を有効化",
     "update_frequency": "更新頻度:",
@@ -337,6 +340,7 @@
   },
   "main_ui": {
     "url_placeholder": "YouTubeの動画URLまたはプレイリストURLを入力",
+    "url_placeholder_generic": "対応サイトの動画またはプレイリストURLを入力",
     "merge_subtitles": "字幕を結合",
     "save_thumbnail": "サムネイルを保存",
     "save_description": "説明を保存",