Media agent for Video JS v5.0.2

Changed

• Video Core: Updated the bundled @newrelic/video-core dependency to v5.1.1 and pinned it to this exact version (previously ^5.1.0), so every build uses the same core release.
• Dependency pinning: dependencies and devDependencies are now pinned to the exact versions already resolved in package-lock.json, so a fresh install no longer picks up newly published releases of build tooling.