fix(deps): update vulnerable Rust dependencies

[chaliy]

What

Update vulnerable Rust dependencies in the Python binding path.

Why

Dependabot reported open PyO3 advisories, and local audit also surfaced a vulnerable quinn-proto transitive dependency.

How

• Bump fetchkit-python PyO3 dependencies from 0.28 to 0.29
• Refresh Cargo.lock for the PyO3 family
• Bump quinn-proto from 0.11.14 to 0.11.16

Risk

• Low
• Dependency-only update; Python binding API still compiles against PyO3 0.29

Checklist

• Unit tests are passed
• Smoke tests are passed
• Documentation is updated or not needed
• Specs are up to date and not in conflict
• cargo audit checked