ci: add license compliance checks and LICENSE-3RD-PARTY.txt generation

[csanx]

Proposed changes

Jira ticket: CLOUDP-424406

Adds license compliance checking and third-party license notice generation for atlas-local-lib-py, covering both dependency ecosystems in the repo (Rust via cargo, Python via pip).

This PR introduces:

• A License compliance workflow (.github/workflows/license.yml) that runs on push and PRs. It enforces the allowed-license policy for Rust deps (cargo deny check licenses) and Python runtime deps (pip-licenses --allow-only), regenerates LICENSE-3RD-PARTY.txt, and fails if the checked-in copy is stale.
• deny.toml, about.toml, and about.hbs to configure cargo-deny and cargo-about for the Rust dependency license policy and notice template.
• scripts/generate-third-party.sh, which concatenates the Rust (cargo-about) and Python (pip-licenses) license notices into a single LICENSE-3RD-PARTY.txt at the repo root.
• scripts/py_runtime_deps.py, to ensure only real runtime deps are checked.
• The generated LICENSE-3RD-PARTY.txt itself.

[Copilot]

Pull request overview

Adds automated license-compliance enforcement and reproducible third-party notice generation for atlas-local-lib-py, spanning both the Rust (cargo) and Python (pip) dependency ecosystems.

Changes:

• Add a GitHub Actions workflow to enforce allowed-license policies and to verify LICENSE-3RD-PARTY.txt is kept up to date.
• Introduce cargo-deny/cargo-about configuration and a Handlebars template for Rust third-party notices.
• Add scripts to compute Python runtime dependency closure and to generate the combined third-party notice file.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
scripts/py_runtime_deps.py	Computes the Python runtime dependency transitive closure from installed distribution metadata.
scripts/generate-third-party.sh	Generates LICENSE-3RD-PARTY.txt by concatenating Rust (cargo-about) and Python (pip-licenses) notices.
LICENSE-3RD-PARTY.txt	Checked-in generated third-party notices output.
deny.toml	Defines Rust dependency allowed-license policy for cargo-deny.
Cargo.toml	Adds crate metadata (authors, license, publish=false) used by licensing/reporting tooling.
about.toml	Configures cargo-about accepted licenses and private crate handling.
about.hbs	Template for Rust third-party license notice output.
.github/workflows/license.yml	CI workflow to enforce license compliance and verify the generated notice file is not stale.

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