refactor: Improved App Core Manager with enhanced startup logic

Significantly enhanced the App Core Manager:

- Refactored the core manager and its startup stages for improved efficiency and maintainability.
- Implemented proper management for data store interactions.
- Removed unused resources to streamline the project.

Author: Mihai-Cristian Condrea

app/src/main/res/values-night/themes.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <style name="AppTheme" parent="Theme.Material3.DynamicColors.DayNight">
+        <item name="windowActionBar">false</item>
+        <item name="windowNoTitle">true</item>
+        <item name="android:windowLightStatusBar">false</item>
+    </style>
+</resources>

app/src/main/res/values-v31/themes.xml

@@ -8,10 +8,4 @@
         <item name="postSplashScreenTheme">@style/AppTheme</item>
         <item name="android:windowSplashScreenIconBackgroundColor">?attr/colorSurface</item>
     </style>
-
-    <style name="AppTheme" parent="Theme.Material3.DynamicColors.DayNight">
-        <item name="windowActionBar">false</item>
-        <item name="windowNoTitle">true</item>
-        <item name="android:windowLightStatusBar">false</item>
-    </style>
 </resources>