build(deps): bump pyo3 to 0.29 for Python 3.15

[liquidsec]

Summary

Bumps pyo3 and pyo3-async-runtimes 0.27 -> 0.29 so the build survives Python 3.15, which ships October 9. Raised by @en0f on #304.

Why this is time-boxed

#304 moved testing and wheels onto the shared workflows, which derive their matrix from requires-python = ">=3.10" instead of a fixed list. 3.15 enters both matrices on release day, and pyo3 0.27 refuses to build against an interpreter it doesn't know:

• python / test (3.15) fails at maturin develop -> python / passed fails -> every PR is blocked, since that's a required check.
• The 3.15 wheel leg fails -> publish.yml stops before PyPI, crates.io and the GitHub release.

Capping requires-python was the other option, but that locks 3.15 users out of installing.

Changes

Cargo.toml and Cargo.lock only — no source changes. python.rs is already on the Bound / Python::attach API that 0.28 and 0.29 require, so nothing in it moved.

	before	after
pyo3	0.27.2	0.29.3
pyo3-async-runtimes	0.27.0	0.29.0

pyo3 0.29.0 is where 3.15 support landed (PEP 820 module init, PyModExport/PyABIInfo); 0.29.3 is the current stable. pyo3-async-runtimes 0.29 requires pyo3 ^0.29, so the two move together.

Validation

$ cargo fmt --all -- --check
$ cargo clippy --all-targets --all-features -- -D warnings
    Finished `dev` profile
$ cargo build --features py
    Finished `dev` profile
$ cargo test --all-features
test result: ok. 13 passed; 0 failed    # lib
test result: ok. 2 passed; 0 failed     # bin + api

No deprecation warnings from the jump.

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