Add kernel full-journey E2E coverage

[tgarciai]

Summary

• add a real kernel full-journey integration test that covers projection, query, compatibility, command, and admin flows
• add a full TLS variant with gRPC mTLS, NATS mTLS, Valkey mTLS, and Neo4j Bolt TLS
• extend the Neo4j adapter to accept a CA path on secure schemes so the graph store can verify the server certificate in tests

Verification

• cargo test -p rehydration-adapter-neo4j
• cargo test -p rehydration-transport-grpc --features container-tests --test kernel_full_journey_integration --no-run
• bash scripts/ci/integration-kernel-full-journey.sh
• bash scripts/ci/integration-kernel-full-journey-tls.sh
• git diff --check

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud