feat: enhance admin page and testing functionality

- Updated admin page to include navigation buttons for month selection, improving user experience.
- Refactored `AdminDutyList` to group duties by date, enhancing the display and organization of duties.
- Improved error handling in `ReassignSheet` by using i18n keys for error messages, ensuring better localization support.
- Enhanced tests for admin page and components to reflect recent changes, ensuring accuracy in functionality and accessibility.
- Added event dispatch for configuration loading in the app configuration, improving integration with the Telegram Mini App.

duty_teller/api/app.py

@@ -169,7 +169,8 @@ def app_config_js() -> Response:
     tz = _safe_tz_string(config.DUTY_DISPLAY_TZ)
     tz_js = f'\nwindow.__DT_TZ = "{tz}";' if tz else "\nwindow.__DT_TZ = undefined;"
     body = (
-        f'window.__DT_LANG = "{lang}";\nwindow.__DT_LOG_LEVEL = "{log_level}";{tz_js}'
+        f'window.__DT_LANG = "{lang}";\nwindow.__DT_LOG_LEVEL = "{log_level}";{tz_js}\n'
+        'if (typeof window !== "undefined") window.dispatchEvent(new Event("dt-config-loaded"));'
     )
     return Response(
         content=body,