feat: implement OAuth authentication

[ahonn]

Replaces the previous API key-based authentication with a full OAuth flow using the Authorization Code Grant with PKCE.

Key changes:

• Implemented an OAuthClientProvider to manage the authentication process.
• The server now automatically initiates a browser-based login for the user to authorize the application.
• Access tokens and refresh tokens are securely stored locally and refreshed automatically.
• Removed the need for users to manage and configure an API key manually, simplifying the setup process.
• Updated all relevant documentation, configurations, and dependencies to support the new authentication mechanism.

[github-actions]

🎉 This PR is included in version 1.3.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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