chore(deps): update reqwest from 0.12 to 0.13 (#12)

## What
Update reqwest dependency from 0.12 to 0.13.

## Why
Keep dependencies up to date with latest stable versions. reqwest 0.13
uses rustls as the default TLS backend with improved certificate
handling.

## How
- Updated `Cargo.toml` to use `reqwest = "0.13"` with simplified
features
- Removed `rustls-tls-native-roots` feature (no longer needed - reqwest
0.13 handles native certificates automatically via
`rustls-platform-verifier`)
- Updated `Cargo.lock` with all transitive dependency changes

## Risk
- Low
- This is a semver-compatible update for the project's public API

### Checklist
- [x] Unit tests are passed
- [x] Clippy passes with no warnings
- [x] Documentation builds without warnings
- [x] Formatting is correct

Co-authored-by: Claude <noreply@anthropic.com>

Author: chaliy