Bootstrap the machine funding Rust workspace

[ameya-deshmukh]

Summary

• introduce the root Cargo workspace and machine-funding crate manifest
• commit the generated lockfile for reproducible binary builds
• keep this dependency-bootstrap PR behavior-free so the manifest and resolution can be reviewed separately

Of the 5,840 added lines, 5,731 are generated Cargo.lock content.

Test plan

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --locked -- -D warnings
• cargo test --workspace --locked
• cargo build --workspace --release --locked

Stack

2 of 4. Depends on #39; next is #41. Split from #35.

Fixes SEI-413 — https://linear.app/seismic-systems/issue/SEI-413/3-machine-funding-bootstrap-the-rust-workspace

[linear-code]

SEI-413