SAST False Positive Detection - Backend - Create audit event

What does this MR do and why?

Adds an audit event for changes to the duo_sast_fp_detection_enabled project setting, and extends the ProjectSettingsUpdate GraphQL mutation to allow users with update_sec_ai_workflow_settings to toggle this setting without requiring admin_project.

This follows the same pattern established for SAST Vulnerability Resolution in !239266 (merged), extending it to False Positive Detection.

This MR closes: SAST False Positive Detection - Backend - Creat... (#603463 - closed) • Charlie Kroon • 19.2 This MR blocks: SAST False Positive Detection – Frontend – Expo... (!241787 - merged) • Charlie Kroon • 19.2

References

• Project epic: SAST False Positive Detection - Add permission ... (gitlab-org#22422 - closed) • Charlie Kroon • 19.2

  • Issue this MR is closing: #603463 (closed)+S
  • Blocks: SAST False Positive Detection – Frontend – Expo... (!241787 - merged) • Charlie Kroon • 19.2

• Reference implementation: !239266 (merged)