Remove redis-py dependency and finalize migration

## Objective

Remove redis-py from project dependencies after completing all migrations.

## Files to modify

- `requirements.txt` (lines 74, 76, 122)
- Remove: `hiredis>=3.0.0`
- Remove: `redis[hiredis]==4.5.5`
- Remove: `types-redis`

## Tasks

- [ ] Verify all redis-py imports have been removed from codebase
- [ ] Search for any remaining `import redis` or `from redis` statements
- [ ] Remove dependencies from requirements.txt
- [ ] Regenerate lock files: `pants generate-lockfiles --resolve=python-default`
- [ ] Export updated virtualenv: `pants export --resolve=python-default`
- [ ] Run full test suite to verify everything works
- [ ] Update documentation if needed

## Dependencies

This task should be done last after all other migration tasks are complete.

## Verification

```bash
# Search for any remaining redis-py usage
grep -r "import redis" src/ --include="*.py"
grep -r "from redis" src/ --include="*.py"
```

## Related

Part of BA-2585 - Retire redis-py entirely. This is the final task.

JIRA Issue: BA-3274