fix: resolve connectivity issues for Android and Web builds

- Android: Added INTERNET permission and enabled cleartext traffic in AndroidManifest.xml.
- Web: Implemented and registered CORSMiddleware in backend to allow cross-origin requests.
- Flutter: Updated SettingsProvider to use 10.0.2.2 as default for Android Emulator for easier local testing.

frontend/android/app/src/main/AndroidManifest.xml

@@ -1,8 +1,10 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <uses-permission android:name="android.permission.INTERNET" />
     <application
         android:label="Hightube"
         android:name="${applicationName}"
-        android:icon="@mipmap/launcher_icon">
+        android:icon="@mipmap/launcher_icon"
+        android:usesCleartextTraffic="true">
         <activity
             android:name=".MainActivity"
             android:exported="true"