fix: Allow asset download from private repos

[markg-github]

Allow asset download from private repos: use URL with asset ID, supply token, etc.
Use --public to download in a way (the old way) that only works for public repos.

Resolves: #18

[Copilot]

Pull request overview

This PR enables downloading release assets from private GitHub repositories by using asset IDs and authentication tokens, while maintaining backward compatibility for public repos via a --public flag.

Key Changes:

• Added authentication support using GitHub tokens for private repository access
• Introduced --public flag to preserve original public-only download behavior
• Modified asset download logic to use asset ID-based URLs for private repos

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/github.rs	Added id field to Asset struct, --public flag, and helper methods for repo metadata and token access
src/http/server.rs	Added authentication headers to HTTP client when accessing private repositories
src/http/service.rs	Implemented request builder with private/public repo logic and response inspection utilities

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

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