[feat] CV validation audit trail

[erikbayerlein]

Epic: #70 (Validação de CV)
Use Case: #65

Fase 2 — Implementação posterior à fase de inscrição.

Description

Store complete audit information for CV validation actions.

Acceptance Criteria

• Each validation action records: validatorId, validatorRole, candidateId, itemId, originalScore, validatedScore, timestamp.
• History of all validation changes is preserved (not overwritten).
• Audit data is queryable for reporting.