apps: settings: Avoid circular dependancies during app init

wasp.system cannot be safely be used from app __init__ methods. Move
the initial value settings to the foreground method instead.

Fixes: b1326e1609 ("apps: settings: Fix initial slider value")
Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

wasp/apps/settings.py

@@ -19,9 +19,9 @@ class SettingsApp():
 
     def __init__(self):
         self._slider = wasp.widgets.Slider(3, 10, 90)
-        self._slider.value = wasp.system.brightness - 1
 
     def foreground(self):
+        self._slider.value = wasp.system.brightness - 1
         self._draw()
         wasp.system.request_event(wasp.EventMask.TOUCH)