samp(py): publish samp-crypto 1.0.0, fix broken samp-core 1.x

[mcjkula]

Summary

• samp-core on PyPI (1.1.0, 1.1.1, 1.2.0) has been uninstallable, it declares a runtime dep on samp-crypto, which was not published.
• Prepares samp-crypto 1.0.0 for PyPI: full pyproject metadata (description, license, classifiers, URLs), README, LICENSE, abi3-py39 wheels (one wheel covers Python 3.9+), 9 cargo unit tests, 3 pytest roundtrip tests, dead #[pymodule] exports pruned (ecdh, hkdf_sha256, chacha20poly1305_*), and .github/workflows/release-py-crypto.yml (trusted publisher, matrix Linux+macOS+Windows + sdist).
• Bumps samp-core to 1.2.1 with samp-crypto==1.0.0 pinned exactly, and adds .github/workflows/release-py-core.yml.

Architecture

Python is the only SAMP SDK with a two-package structure. Rust (schnorrkel), TypeScript (@polkadot/wasm-crypto), and Go (ChainSafe/go-schnorrkel) all have in-language sr25519; Python has none, so the PyO3-wrapped Rust crypto lives in a separate maturin-built package.

Release sequence (post-merge)

1. samp-crypto Trusted Publisher pre-registered on PyPI.
2. pypi GitHub environment created.
3. Tag samp-crypto/v1.0.0 pushed first.
4. After samp-crypto is live, tag samp-core/v1.2.1.

Test plan

• cargo test --lib: 9/9 passing.
• maturin build --release: produces
  samp_crypto-1.0.0-cp39-abi3-*.whl.
• maturin develop: works locally.
• python -m pytest python/tests/ python/samp-crypto/tests/: 210/210
  passing.
• python -m build for samp-core: produces sdist + universal wheel.