Refactor color scheme handling to use a fixed 'dark' theme and implement SourceSelectionModal for source management in the player

hooks/useThemeColor.ts

@@ -3,15 +3,13 @@
  * https://docs.expo.dev/guides/color-schemes/
  */
 
-import {useColorScheme} from 'react-native';
-
 import {Colors} from '@/constants/Colors';
 
 export function useThemeColor(
   props: {light?: string; dark?: string},
   colorName: keyof typeof Colors.light & keyof typeof Colors.dark,
 ) {
-  const theme = useColorScheme() ?? 'dark';
+  const theme = 'dark';
   const colorFromProps = props[theme];
 
   if (colorFromProps) {