feat(i18n): add full Italian locale support and enable it in language selector

This commit introduces complete Italian localization for Noctalia shell and wires the locale into the runtime language list.

Changes included:
- Added new translation file: Assets/Translations/it.json
- Localized the full string tree used by the shell UI, including:
  - common labels and shared terms
  - bar and widget settings
  - launcher, lock screen, notifications, wallpaper, weather, setup, tooltips
  - all settings panels and sub-panels (audio, display, dock, plugins, user interface, hooks, OSD, desktop widgets, color scheme, etc.)
- Preserved all runtime placeholders and markup tokens (e.g. {count}, {name}, <br>, <i>, <b>, )
- Enabled Italian in the language registry by updating Commons/I18n.qml availableLanguages

Validation and consistency checks:
- Verified JSON validity of Assets/Translations/it.json
- Verified placeholder parity against English source to avoid interpolation regressions
- Ensured translation key structure matches en.json so fallback behavior remains intact

Result:
- Italian (it) is now selectable from Region settings and loads as a first-class locale.

Commons/I18n.qml

@@ -14,7 +14,7 @@ Singleton {
   property string systemDetectedLangCode: ""
   property string fullLocaleCode: "" // Preserves regional locale variants
   // Static list of available translations — update when adding/removing translation files
-  property var availableLanguages: ["en", "de", "es", "fr", "hu", "ja", "ko-KR", "ku", "nl", "nn-HN", "nn-NO", "pl", "pt", "ru", "sv", "tr", "uk-UA", "zh-CN", "zh-TW"]
+  property var availableLanguages: ["en", "de", "es", "fr", "hu", "it", "ja", "ko-KR", "ku", "nl", "nn-HN", "nn-NO", "pl", "pt", "ru", "sv", "tr", "uk-UA", "zh-CN", "zh-TW"]
   property var translations: ({})
   property var fallbackTranslations: ({})