UI: use background color for navbar in dark mode

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

app/src/main/res/values-night-v27/styles.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <style name="AppTheme" parent="Theme.AppCompat.DayNight.DarkActionBar">
+        <item name="colorAccent">@color/accent</item>
+        <item name="android:navigationBarColor">?android:attr/colorBackground</item>
+    </style>
+
+</resources>