Add configuration files and update authentication service error handling

- Introduced .vscode/settings.json and .vscode/launch.json for IDE configuration.
- Updated DebugAuthInterface and ArcaneAuthenticationService to return const Result.ok() for consistency.
- Added ArcaneTheme class for theme management.
- Updated pubspec.yaml to change result_monad dependency version.
- Modified authentication_service_test to return const Result.ok() in mock setups.

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

.vscode/settings.json

@@ -0,0 +1,4 @@
+{
+    "dart.flutterSdkPath": "/Users/hans/.puro/envs/stable/flutter",
+    "dart.sdkPath": "/Users/hans/.puro/envs/stable/flutter/bin/cache/dart-sdk"
+}