uUR: build on MicroPython 1.27 while keeping pre-1.19 (MaixPy) support

[kdmukAI-bot]

The uUR binding uses the pre-v1.19 MicroPython C API, so it does not compile on
MicroPython >= 1.19 (e.g. 1.27). This makes it build on both the modern and the
pre-1.19 (MaixPy-era, used by Krux) API in a single file.

MicroPython's v1.19 "type slots" refactor changed three things the binding uses:
type definitions (flat struct -> MP_DEFINE_CONST_OBJ_TYPE), finaliser
allocation (m_new_obj_with_finaliser -> mp_obj_malloc_with_finaliser), and
MP_REGISTER_MODULE arity (3 args -> 2).

uUR.c:

• MP_ERROR_TEXT: #ifndef fallback to the raw string on builds that predate it.
• Finaliser: define mp_obj_malloc_with_finaliser in terms of the legacy
  m_new_obj_with_finaliser when absent, so the call sites use one spelling.
• Type definitions and MP_REGISTER_MODULE: #if defined(MP_DEFINE_CONST_OBJ_TYPE)
  selects modern vs legacy; the legacy branch is the existing code verbatim.
• The unused result / expected_part_count / processed_parts_count method
  objects (these values are exposed as attributes) compile only on the legacy
  path; newer toolchains reject them under -Werror=unused-const-variable.

CMakeLists.txt (ESP-IDF component):

• Add src/types/bip39.c, which uUR.c references but was missing from SRCS.
• REQUIRES mbedtls only. mbedtls_compat is absent on ESP-IDF 5.5.x, and
  tests/esp-idf-smoke already requires only mbedtls.

The legacy (< v1.19) path is unchanged from the current code, so existing
consumers are unaffected.

Tested: builds on MicroPython 1.27 with ESP-IDF 5.5.x (ESP32-P4); uUR.URDecoder
decodes a multi-part crypto-psbt UR to the expected CBOR on-device. Not built
against a pre-v1.19 MicroPython — cUR's CI does not build uUR.c today (it is
clang-format checked only; the pc and esp-idf jobs build the C library). A
job compiling uUR.c as a USER_C_MODULE against a modern and a pre-v1.19
MicroPython would cover both paths.