SAST False Positive Detection - Add permission AppSec Team to enable FP
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## TL;DR
Extend the Security Manager permission model to allow Security Managers to toggle SAST False Positive Detection settings at the project level, without requiring Maintainer/Owner roles.
We want to replicate the same pattern established for SAST VR (https://gitlab.com/groups/gitlab-org/-/work_items/21971 and https://gitlab.com/gitlab-org/gitlab/-/merge_requests/239266)
## Scope
### In Scope
* Extend `update_sec_ai_workflow_settings` permission to cover `duo_sast_fp_detection_enabled` setting
### Out of Scope
* Secret Detection False Positive Detection (`duo_secret_detection_fp_enabled`)
* Group/subgroup/organization/instance level configuration (covered by [&21766](https://gitlab.com/groups/gitlab-org/-/work_items/21766))
* Custom roles support for the permission
* Changes to the Vulnerability Details page FP detection action button
* New permissions or roles beyond what was established for SAST VR
* Redesigning the GitLab role model
## Phase
This is Iteration 2 of the parent epic, following the SAST VR permission work completed in Iteration 1.
**Epic Phase:** Phase 2
**Parent Epic:** https://gitlab.com/groups/gitlab-org/-/work_items/21725+s
## Problem Statement
Security Managers can now toggle SAST Vulnerability Resolution settings (per [&21971](https://gitlab.com/groups/gitlab-org/-/work_items/21971)), but they still cannot enable/disable SAST False Positive Detection without Maintainer/Owner access. With this epic we are creating the permission for them to do this.
## Proposed Approach
Replicate the exact pattern established in [gitlab!239266](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/239266):
## Feature Flag
- [X] Required
**Flag name:** `update_false_positive_setting_permission`
**Default state:** Enabled / Disabled
**Rollout plan:** Optional gradual rollout details.
## Success Criteria
Define outcomes that prove this deliverable is complete.
- [ ] Criterion 1
- [ ] Criterion 2
## Dependencies
- Blocked by: #issue
- Blocks: #issue
## Implementation Notes
Keep this updated as work progresses.
## Open Questions
| Question | Owner | Status |
|-----------|--------|--------|
## Resources
- Design: [link]
- Documentation: [link]
- Relevant issues, discussions etc.
epic