Adds a `LICENSES/` directory with SPDX-named copies of the existing license texts (`MIT.txt`, `Apache-2.0.txt`) per the [REUSE Specification](https://reuse.software/spec/).
## Why
Automated license scanners (the OpenSSF Best Practices BadgeApp, GitHub's license API, REUSE tooling) look for a top-level `LICENSE`/`COPYING` file or a `LICENSES/` directory with SPDX-named files. Our files are named `LICENSE-MIT` / `LICENSE-APACHE` (Rust convention), which these scanners do not recognize — so the BadgeApp's `license_location` check keeps auto-flipping to "Unmet".
## What
- New `LICENSES/MIT.txt` — byte-identical copy of `LICENSE-MIT`
- New `LICENSES/Apache-2.0.txt` — byte-identical copy of `LICENSE-APACHE`
- Existing `LICENSE-MIT` and `LICENSE-APACHE` are **unchanged**
The project remains dual-licensed under **MIT OR Apache-2.0**. This change is additive only.
kingchenc