Add ability to remove False Positive flag from vulnerabilities

Summary

Add functionality to allow users to remove the False Positive (FP) flag from vulnerabilities that were previously marked as false positives, enabling them to revert vulnerabilities back to their original detected state.

Problem

Users need the ability to:

• Correct mistakes when vulnerabilities were incorrectly marked as false positives
• Re-evaluate vulnerabilities when code context changes
• Handle cases where AI suggestions were incorrect
• Maintain accurate vulnerability state management

Requirements

User Interface

• Remove FP Action: Clear action to remove false positive designation
• Confirmation Dialog: Prevent accidental removal with confirmation step
• Reason Capture: Optional field to capture why FP flag is being removed
• State Transition: Clear indication of vulnerability returning to "detected" state

User Experience Flow

1. User navigates to vulnerability with FP flag
2. User selects "Remove False Positive" action
3. Vulnerability state transitions back to "detected"
4. UI updates to reflect new state
5. Audit log records the action