Feat/improve design

[AdamLBS]

This pull request introduces several important updates, including the addition of a new Node model and node-fetching logic, as well as significant improvements to the build and release automation for multiple platforms. It also updates the Flutter SDK version used throughout the project.

Build and Release Automation:

• Added a comprehensive GitHub Actions workflow (.github/workflows/build.yml) to automate building and releasing the application for Android, Windows, and macOS, including artifact uploads and GitHub Releases.

Node Model and Fetching Logic:

• Introduced a new Node model in lib/models/node.dart, with fields for node metadata and a fromJson factory for parsing API responses. Also added a parseNodes utility function.
• Added a fetchNodes function in lib/data/node/node_connection.dart to retrieve a list of nodes from the HushNet registry API and parse them into Node objects.
• Updated imports in lib/data/node/node_connection.dart to include the new Node model.

Flutter SDK Version Update:

• Updated the Flutter SDK version to 3.41.0 in .fvmrc and .vscode/settings.json to ensure consistency across development and CI environments. [1] [2]