NightLight: refactored the code to make simpler

- using intensity instead of warmth
- animated color transition
- removed unecessary bindings and double properties
- using better icons to avoid confusion with brightness
- polished settings UI

shell.qml

@@ -40,7 +40,6 @@ ShellRoot {
   ScreenCorners {}
   Bar {}
   Dock {}
-  NightLight {}
 
   Notification {
     id: notification
@@ -52,6 +51,8 @@ ShellRoot {
 
   ToastOverlay {}
 
+  NightLightOverlay {}
+
   IPCManager {}
 
   // ------------------------------