refactor: reduce duplication and improve readability of settings page

The settings page ([lib/app/modules/settings/views/](https://github.com/CCExtractor/taskwarrior-flutter/tree/main/lib/app/modules/settings/views)) has significant code duplication and readability
issues:

- Repeated section boilerplate - _buildSectionHeader() and _buildSettingsCard() are called manually for
every settings group with the same styling logic.
- Near-identical toggle widgets - 4 separate files (settings_page_on_task_start_list_tile_trailing.dart,
settings_page_on_task_create_list_tile_trailing.dart, settings_page_highlist_task_list_tile_trailing.dart,
settings_page_enable_24hr_format_list_tile_trailing.dart) each containing ~30 lines that all do the same
thing: Obx(() => Switch(...)).
- Hardcoded language names - _getLanguageName() duplicates what should be part of the SupportedLanguage enum, requiring updates in multiple places when a language is added.
- Large inline widgets - The delete-tasks confirmation dialog (~80 lines) is inlined directly in the body,
hurting readability.

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Proposed Changes

1. Introduce SettingsGroup widget + SettingsItemConfig sealed class
A single reusable widget that accepts title, icon, and a List and handles section
header, card styling, and dividers internally. Three item types:
- SettingsToggleItem - title, subtitle, RxBool value, optional prefsKey (auto-saves to SharedPreferences),
optional onChanged for extra side effects
- SettingsDropdownItem - title, subtitle, Rx value, options list, labelBuilder, onChanged
- SettingsCustomItem wraps any custom widget

2. Add nativeName getter to SupportedLanguage
Centralizes display names so Dart's exhaustive switch enforces updates when new languages are added.

3. Extract delete-tasks tile into SettingsPageDeleteTasksTile
Moves the FutureBuilder + confirmation dialog into its own widget file.

4. Delete absorbed files
Remove the 5 single-purpose trailing widget files whose logic is now handled by SettingsGroup.

Start in lib/app/modules/settings/views/ and read the settings page plus the four listed toggle trailing files. Trace SupportedLanguage and the inline delete-tasks confirmation before planning the shared SettingsGroup, language-name getter, and extracted delete-tasks tile. Done means repeated section and toggle logic is consolidated, language names have one source, the dialog is extracted, and the five absorbed files are removed.

Written by the indexing model from the issue text.