Fixes#20128
## Summary
Fix REST API filter parsing when bare filters are mixed with explicit
conjunctions.
## What changed
- Replaced the loose parentheses check in
`addDefaultConjunctionIfMissing` with proper root conjunction detection.
- Shared the root conjunction regex with `parseFilter`.
- Added regression tests for mixed filters like
`status[eq]:'TODO',and(title[ilike]:'%test%')`.
## Validation
- `npx nx test twenty-server
--testPathPatterns=add-default-conjunction.util.spec.ts --runInBand
--coverage=false`
- `npx prettier --check ...`
Sri Hari Haran Sharma
281eaa3721