Update Result to Dart 3 and workflows

[kmartins]

• Updated Dart SDK to ^3.6.0 and dependencies.
• Refactored Result to a sealed class with Success and FailureResult subclasses to utilize Dart 3 features.
• Updated onSuccess and onFailure to return void to comply with avoid_returning_this lint, requiring cascade notation usage.
• Added @immutable annotations to Failure, Success, and FailureResult.
• Updated workflows to use @v1 tag.
• Fixed various lint issues and documented necessary ignores.

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PR created automatically by Jules for task 658926196224835860 started by @kmartins

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