android: fix navigation bar always being bright even in dark mode (#3464)

Right now both light mode and dark mode get light navigation bar, and
looks jarring in the dark modes.

This commit applies a more appropriate color before the UI thread
runs (in app config), as well as applying the current theme background
after the UI shell is mounted.

This should fix #3332.

Co-authored-by: Hailey <me@haileyok.com>

app.config.js

@@ -95,6 +95,11 @@ module.exports = function (config) {
         barStyle: 'light-content',
         backgroundColor: '#00000000',
       },
+      // Dark nav bar in light mode is better than light nav bar in dark mode
+      androidNavigationBar: {
+        barStyle: 'light-content',
+        backgroundColor: DARK_SPLASH_CONFIG_ANDROID.backgroundColor,
+      },
       android: {
         icon: './assets/icon.png',
         adaptiveIcon: {