fix(dm): null-safe columnType comparison in DMMetaData

[Aias00]

Related issue

Closes #2150

Summary

DMMetaData.columns called columnType.toUpperCase() without a null guard; if TYPE_NAME was null, NPE. Changed to StringUtils.equalsIgnoreCase (null-safe), mirroring OscarMetaData.

Verification

• mvn compile -> BUILD SUCCESS.

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AI assistance: The fix, verification, and PR description were produced with Claude Code assistance.

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[openai0229]

StringUtils.equalsIgnoreCase is null-safe and the implementation direction is correct, but this PR is not ready to merge without an automated regression test.

Please add a DMMetaData test with a metadata row whose column type is null to prove there is no exception, plus a mixed-case TIMESTAMP row to prove the existing column-size behavior is preserved. Rebase onto the latest main before requesting another review; #2198 also changes this class and will need to be coordinated.