feat(python): add a CPython binding + build for the uUR module

[kdmukAI-bot]

Add a CPython binding for the uUR module

This adds a CPython counterpart to the existing MicroPython uUR.c wrapper, so the native BC-UR encoder/decoder is importable as uUR on host/desktop CPython (e.g. Raspberry Pi), mirroring the module the ESP32/MicroPython firmware already exposes. Business logic that does import uUR then works identically on both runtimes.

What's here

• python/uUR.c — the full uUR surface via the CPython C-API: UR, URDecoder, UREncoder, FountainEncoder, the Types CBOR-codec namespace (bytes/psbt/bip39/output + tag/type constants), and the DECODER_* state constants. It wraps the ur_decoder_get_state() state-machine API and returns the FountainEncoder view uncached (leak-free under refcounting; avoids a parent↔view reference cycle — behaviorally identical to the cached MicroPython view).
• setup.py + pyproject.toml — a pip-installable build of the uUR extension from the portable core (envelope + types + the bundled SHA-256; no OpenSSL/mbedTLS). py-modules = [] keeps setuptools from misreading the C src/ dir as a Python src-layout package.
• .gitignore — ignore the CPython build artifacts.

Notes

• Host build uses the bundled src/sha256/sha256.c (UR_USE_MBEDTLS_SHA256 unset), so there's no external crypto dependency.
• Kept intentionally in sync with the module contract of uUR.c so the two runtimes present one API.

Validation

• pip install . builds + imports cleanly; a full multi-part fountain encode→decode roundtrip plus the Types codecs pass on x86-64 CPython 3.13 and, on-device, on ARMv6 CPython 3.10 (Raspberry Pi Zero).

🤖 Generated with Claude Code