fix(deps): update reqwest feature for v0.13 compatibility (#12)

## Summary

- Change `rustls-tls` to `rustls` (renamed in reqwest 0.13+)
- Track `Cargo.lock` for reproducible CI builds with `--locked` flag
- Enables CI to use `cargo build --locked` for consistent, reproducible
builds

## Changes

1. **Cargo.toml**: Updated reqwest feature from `rustls-tls` to `rustls`
2. **.gitignore**: Removed `Cargo.lock` from ignore list (now tracked)
3. **Cargo.lock**: Added for reproducible builds

## Test plan

- [x] `cargo build` compiles successfully
- [ ] CI passes with `--locked` flag
- [ ] All existing tests pass

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Len P. van der Hof <Lenvanderhof@ReasonKit.sh>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

ReasonKit Web v0.1.5

fix(web): exclude brand assets from crates.io package (size limit)