fix: revert DB driver to static imports, fix test regressions
- Revert createRequire() for DB drivers — require() can't resolve .ts
files in Vitest, breaking 49 test suites
- Make cache invalidation fail-safe via try-catch around revalidateTag
(throws outside Next.js context: tests, tasks service, websocket)
- Fix 6 integration test imports: barrel no longer exports concrete
classes, point tests at direct source paths
- Fix Redis cache handler lint errors: remove non-null assertions,
suppress __NEXT_BUILD_ID underscore warning