build(deps): Update flutter_web_auth_2 to v6 with built-in Kotlin support

Upgrade flutter_web_auth_2 from ^5.0.3 to ^6.0.0-alpha.4 to resolve
the 'plugins that apply Kotlin Gradle Plugin' build warning.
This new version migrated to built-in Kotlin support as required by
Flutter SDK >=3.44.0.

Fixes #kotlin-gradle-plugin-warning

pubspec.lock

@@ -135,18 +135,18 @@ packages:
     dependency: "direct main"
     description:
       name: flutter_web_auth_2
-      sha256: "8f9303471dcd96670878c9b7c0c4e14c37595b2add67465f6a868f17a5872dfc"
+      sha256: f702216bf258a5bae9ec5bcf2b77f7932838b6be53b4a97c8719665067ec11ba
       url: "https://pub.dev"
     source: hosted
-    version: "5.0.3"
+    version: "6.0.0-alpha.4"
   flutter_web_auth_2_platform_interface:
     dependency: transitive
     description:
       name: flutter_web_auth_2_platform_interface
-      sha256: ba0fbba55bffb47242025f96852ad1ffba34bc451568f56ef36e613612baffab
+      sha256: "6d3f35c0435225f31c9734be69cb5ce6f4fad194d6648b00c10eaf5a844837c9"
       url: "https://pub.dev"
     source: hosted
-    version: "5.0.0"
+    version: "6.0.0-alpha.2"
   flutter_web_plugins:
     dependency: transitive
     description: flutter
@@ -593,10 +593,10 @@ packages:
     dependency: transitive
     description:
       name: window_to_front
-      sha256: "14fad8984db4415e2eeb30b04bb77140b180e260d6cb66b26de126a8657a9241"
+      sha256: e1cf0c17b18328da974d54aa783187c5a5fdc1e91d3c939f9b262d8d71d91454
       url: "https://pub.dev"
     source: hosted
-    version: "0.0.4"
+    version: "0.1.2"
   xdg_directories:
     dependency: transitive
     description: