[Backend] Add default SAST profile
We need to add a new default SAST profile that will be automatically available (without requiring any additional steps)
### Requirements
- The profile should be automatically available in the list of available profiles
- No user action should be required to access this profile
- The profile should include the following pipeline triggers:
- `default_branch_pipeline` - Triggers SAST scans on the default branch pipelines
- `merge_request_pipeline` - Triggers SAST scans on merge request pipelines
### Acceptance Criteria
- [ ] Profile appears in available profiles list automatically
- [ ] Profile includes `default_branch_pipeline` trigger
- [ ] Profile includes `merge_request_pipeline` trigger
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