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>

example/.vscode/launch.json

@@ -0,0 +1,25 @@
+{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "example",
+      "request": "launch",
+      "type": "dart"
+    },
+    {
+      "name": "example (profile mode)",
+      "request": "launch",
+      "type": "dart",
+      "flutterMode": "profile"
+    },
+    {
+      "name": "example (release mode)",
+      "request": "launch",
+      "type": "dart",
+      "flutterMode": "release"
+    }
+  ]
+}