Integrate CreateScalingGroup Action with existing GraphQL implementation

## Objective

Complete Create action with GraphQL integration and comprehensive tests.

## Implementation Details

- GraphQL mutation modification (~30 lines)
- `CreateScalingGroupInput` → `Creator` conversion logic
- `simple_db_mutate_returning_item` → `processors.scaling_group.create.wait_for_complete()`
- ScalingGroupOpts conversion logic cleanup (~20 lines)
- Additional Unit tests:
- `test_create_scaling_group_service.py` (~80 lines)
- `test_create_scaling_group_repository.py` (~100 lines)
- Edge case tests (duplicate name, validation, etc.) (~50 lines)

## Estimated Lines

~280 lines

## Dependencies

- Story 3: CreateScalingGroup Action - Creator Spec

## Acceptance Criteria

- [ ] GraphQL mutation uses new processor pattern
- [ ] Input conversion properly handles all fields including ScalingGroupOpts
- [ ] Edge cases tested (duplicate names, invalid inputs)
- [ ] All unit tests pass
- [ ] Legacy `simple_db_mutate_returning_item` removed from CreateScalingGroup

JIRA Issue: BA-3485