Can the switch depend on e.g. Civil Twilight as well?

**Describe the enhancement or feature you'd like**

The from sunrise/sunset (location/coordinates) times don't match when there's actually enough ambient light outside. The sun illuminates the sky significantly before astronomical sunrise and after sunset.

Add an option to use e.g. civil twilight times (sun at -6° below horizon) instead of astronomical sunrise/sunset (sun at 0°).

Civil twilight represents when there's enough natural light for outdoor activities without artificial lighting, making it a more accurate trigger for theme switching.

https://www.timeanddate.com/astronomy/civil-twilight.html

- Civil twilight can start **30-60+ minutes before sunrise** (varies by latitude and season)
- At high latitudes (like Nordic countries), the difference is even more pronounced

**Describe alternatives you've considered**

- Fixed time offsets don't work because twilight duration varies throughout the year

**Additional context**
Add any other context or screenshots about the feature request here.

_Searched: https://github.com/AutoDarkMode/Windows-Auto-Night-Mode/issues?q=is%3Aissue%20civil%20twilight_

Start by locating the code that calculates sunrise and sunset times and the entry point that schedules theme switching. Determine how a user-selectable civil-twilight mode would fit alongside the existing location-based timings; done means the switch can use civil twilight rather than sunrise/sunset, including at varying latitudes and seasons.

Written by the indexing model from the issue text.