feat(contract): detect unchanged status in apply

[Piskoo]

Summary

• Contracts now report whether an apply actually changed anything
• When a contract is applied and its content hasn't changed, the response includes unchanged: true
• Both wf contract apply and the top-level apply command now show Contract/ applied or Contract/ unchanged

Example

$ chainloop  apply -f ./contracts/
WRN API contacted in insecure mode
INF Contract/test-attestation-phases-2 applied
INF Contract/different-name2 unchanged
INF Contract/new-test applied

[cubic-dev-ai]

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