[Aikido] Implement SHA256 digest verification for native binary artifacts

[aikido-autofix]

This patch addresses the security risk of unverified native release artifacts by implementing mandatory SHA256 digest verification against repository-controlled trusted digests. The fix introduces a centralized binary_digests.txt file containing verified SHA256 hashes for all zen-internals binaries, validation scripts that verify cached binaries before use, and a pre-commit hook to prevent accidental commits of unverified digests. The Makefile has been updated to enforce digest validation during the build process, and helper scripts (compute_binary_digests.py and init_digests_from_upstream.py) enable secure initialization and maintenance of the digest registry. Builds will now fail if binary verification fails or required digests are missing, ensuring supply chain integrity.

✅ 1 issue fixed by this PR

Issue	Severity	Description
CodeAudit#811708058	HIGH	make binaries downloads both shared libraries and .sha256sum sidecars, but the Makefile never consumes the sidecars or compares the libraries with repository-controlled digests. check_binaries also treats any existing cache directory as valid, allowing stale or modified artifacts to bypass downloading. make build copies the cache into aikido_zen/libs, Poetry includes that directory in wheels and source distributions, and the runtime passes the selected library to ctypes.CDLL. The publish workflow invokes make build before publishing, establishing a supply-chain path from an unverified upstream artifact to native-code execution in downstream applications.