Remove unused web assets and Windows runner files

- Deleted favicon and icon images from the web directory.
- Removed index.html and manifest.json files from the web directory.
- Cleared out all Windows runner files including CMakeLists.txt, resource files, and source code.
- This cleanup reduces the project size and removes unnecessary components.

android/app/build.gradle.kts

@@ -24,7 +24,7 @@ android {
         applicationId = "com.example.travel_mate"
         // You can update the following values to match your application needs.
         // For more information, see: https://flutter.dev/to/review-gradle-config.
-        minSdkVersion 21
+        minSdk = flutter.minSdkVersion
         targetSdk = flutter.targetSdkVersion
         versionCode = flutter.versionCode
         versionName = flutter.versionName