FINERACT-1659: Fix optimistic locking in savings interest posting batch job

[awaneetdecoder]

Problem

The savings interest posting batch job could post duplicate interest
when two instances ran concurrently. PR #5550 attempted a fix but
adamsaghy correctly identified there was no rollback mechanism —
version mismatch was silently skipped.

Fix

• SQL uses WHERE id=? AND version=? to detect concurrent modification
• version = version + 1 increments on each successful update
• updateCounts[i] == 0 detected as concurrent modification
• ConcurrentModificationException thrown on version mismatch
• @transactional on postInterest() rolls back entire batch

Files Changed

• SavingsAccountData.java — added version field
• SavingsAccountReadPlatformServiceImpl.java — reads version from DB
• SavingsSchedularInterestPoster.java — core fix
• SavingsSchedularInterestPosterTest.java — unit tests
• SavingsInterestPostingJobIntegrationTest.java — integration tests

Fixes FINERACT-1659
Supersedes PR #5550