dx: Implement contract version registry with upgrade tracking

[nanaf6203-bit]

Description

There is no system to track which versions of contracts are deployed where. Create an on-chain version registry.

Acceptance Criteria

• Create VersionRegistry contract in contracts/version-registry/
• Register contract deployments: contract_name, version, code_hash, deployed_at, deployer
• Add register_deployment(name, version, code_hash) message
• Add get_latest_version(name) query
• Add get_deployment_history(name) query
• Integrate with deploy.sh to auto-register on deployment
• Emit ContractDeployed event with version info
• Test: register and query deployment records