refactor: Update README for asset paths and build command

- Changed asset paths for Google Play and App Store badges to point to the correct directory.
- Updated the demo GIF path to reflect the new location in the screenshots folder.
- Modified the build command in the setup instructions to use 'dart run' instead of 'flutter pub run' for better compatibility.
- Removed outdated demo GIF and store badge images that are no longer needed.

android/app/src/debug/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+  <background android:drawable="@mipmap/ic_launcher_background"/>
+  <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
+  <monochrome android:drawable="@mipmap/ic_launcher_monochrome"/>
+</adaptive-icon>