20260908

Bump dart_bridge to 1.9.0 (#41)

dart_bridge 1.9.0 adds serious_python_hard_exit, which terminates the process
without running atexit handlers or C++ static destructors.

Embedders were seeing a SIGSEGV on exit: the interpreter runs on a detached
thread that may still be executing native extension code when the host quits,
and a normal exit() runs __cxa_finalize, destroying the C++ statics inside
every loaded extension module out from under it. The reported case died in
matplotlib's ft2font looking up a pybind11 type-caster map that had just been
destructed.

No Python versions change. This re-release exists to publish the updated
manifest so serious_python can regenerate its version tables against it.

See flet-dev/dart-bridge#20.