Add configurable Sunline, countdown, and moving sky widgets

[coffee-cup]

Add configurable Sunline, Sun Countdown, and Now widgets, and refresh the existing Next Sun Event widget.

• Choose a city and colour theme independently for each widget.
• Show a full-day sun curve, sunrise/sunset times, and daylight change from yesterday, including polar day/night and daylight continuing across midnight.
• Keep a fixed centre line in Now while the sky gradient shifts through the day.
• Use clearer typography and fixed placeholder shapes.

Validated with 33 local unit tests and Device Hub checks of all seven Home Screen gallery layouts, location/theme configuration, and light and tinted appearances. WidgetKit controls delivery of the scheduled updates.

Screenshots

Captured in Device Hub with light appearance.

Sunline, small	Sunline, medium

Sun Countdown	Now

Location and theme