feat: US-40101 CRA mandatory field validation with auto-hold for incomplete records

[saifrazabc]

Description

Implemented CRA mandatory field validation for batch addition (US 40101). Added S1 (manual add with incomplete records response) and S2 (auto-batch with auto-hold for incomplete records). Pure validator function validates 6 always-required fields plus conditional/transaction-specific fields with per-contact specific missing field reasons.

S1 (Manual Add): User adds incomplete contacts → returns incomplete records array with specific missing fields
S2 (Auto-batch): System auto-batches incomplete contacts → automatically puts them on hold with per-contact reasons

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Automated/Unit tests

npm test -- src/api/batches/cra-fields-validator.spec
npm test -- src/api/batches/batches.service.spec
npm test -- src/sync/eligibility/auto-batch.service.spec

Checklist
 I have tested my changes locally
 The code builds and passes all tests, no warnings
 I have made corresponding changes to the documentation (validator comments, service comments)
 All 1150+ tests passing with no failures