Bump to 4.3.2: python-build 20260712 (Android mimalloc seccomp crash, mobile _pyrepl restored)

[FeodorFitsner]

Re-pins the bundled python-build snapshot to 20260712 and bumps all six packages to 4.3.2. No serious_python code changes since v4.3.1 — this is purely the runtime snapshot bump.

The snapshot delivers flet-dev/python-build#29, fixing two on-device startup crashes for Python 3.13/3.14 apps (3.12 unaffected; bundled Python 3.12.13 / 3.13.14 / 3.14.6 and dart_bridge 1.5.0 are unchanged):

• Android: 3.13/3.14 apps died with SIGSYS at dlopen() of libpython on x86_64/x86/armeabi-v7a — mimalloc's allocator-init raw open(2) syscall is forbidden by bionic's seccomp policy; now patched to SYS_openat(AT_FDCWD, …).
• iOS (and Android): _pyrepl is no longer pruned from the mobile stdlib — Python 3.14's pdb imports it at module load, so anything importing pdb (e.g. pytest's debugging plugin) died with ModuleNotFoundError: No module named '_pyrepl'.

Version tables regenerated with dart run serious_python:gen_version_tables --release-date 20260712 (only the release date moved) and verified idempotent with the no-arg form.