COSE receipt verification in C++ API

[maxtropets]

Two items of #7401.

This adds

• a (private) unified C++ API for decoding COSE-formatted CCF receipts.
• a public C++ API to verify COSE-receipt against the current service identity
  • as explained in the umbrella ticket, this will be advanced once pulling up previous identities on the startup gets resolved.

Hence

• decoding + unit test
• verifying + end to end test: extended merkle-proof one, now verifies receipt and all its proofs (+cddl)

[Copilot]

Pull request overview

This PR adds C++ APIs for decoding and verifying COSE-formatted CCF receipts. It introduces a private unified C++ API for decoding receipts and a public API to verify receipts against the current service identity.

Key Changes:

• New decode_ccf_receipt() function for parsing COSE receipts with Merkle proof validation
• New public verify_cose_receipt() API for signature verification against network identity
• Extended end-to-end tests to verify receipts and validate CDDL compliance for all proofs

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/node/cose_common.h	Implements COSE receipt decoding with Merkle proof parsing and root recomputation
src/node/historical_queries_utils.cpp	Implements public verification API using decoded receipts
src/node/node_state.h	Updates to use new decoding API instead of extracting issuer/subject directly
include/ccf/historical_queries_utils.h	Exposes public verify_cose_receipt() API
samples/apps/logging/logging.cpp	Adds /log/public/verify_cose_receipt endpoint
tests/e2e_logging.py	Extends test to verify COSE receipts with positive and negative test cases
src/crypto/test/cose.cpp	Adds unit test for receipt decoding
doc/schemas/app_openapi.json	Adds OpenAPI schema for new endpoint
CHANGELOG.md	Documents the new API

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.