Feat: GitHub Actions workflow for linting and tests

[tripledoublev]

• clippy fixes
• github action for linting and testing
• new test cleanup method

[Copilot]

Pull Request Overview

This PR applies Clippy lint fixes, introduces a GitHub Actions workflow for linting and testing, and adds a shared test cleanup helper along with enhanced retry logic for test setup.

• Remove redundant module nesting and fix import paths for get_backend
• Adjust parameter passing for create_veilid_cryptokey_from_base64 and combine nested conditions
• Refactor tests to add wait_for_public_internet_ready and cleanup_test_resources, and update cleanup calls

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/server.rs	Flatten module structure by removing pub mod server
src/repos.rs	Fix imports for get_backend, remove & on calls, add unused anyhow::Result import
src/media.rs	Same import/path fixes as repos, consolidate conditionals, change handler return type
src/logging.rs	Use $crate in macro for proper hygiene
src/lib.rs	Extensive test refactoring: new helpers, assertions, cleanup
src/groups.rs	Fix imports, add explicit type annotation for Vec
README.md	Add API endpoint documentation
.github/workflows/lint_and_test.yml	New GitHub Actions workflow for Clippy and tests