Add validation for missing dbAdapter option

[Bitshifter-9]

• Add defensive check to prevent crashes when dbAdapter is undefined/null
• Throw clear error message when dbAdapter is missing in non-dbUrl/inMemory mode
• Add test case to verify error handling for missing dbAdapter
• All 223 tests passing with 100% coverage

[divyanshsaraswat]

Hi maintainers, I’d like to work on this issue. I’ve already started implementing a fix and will submit a PR soon.