Add more friction to second deletion step in modal

Problem Statement

Users are sometimes accidentally permanently deleting projects and groups, requiring 2-4 days for GitLab support to recover the data. We need to add an additional checkpoint to the permanent deletion flow to prevent accidental data loss.

Implementation Requirements

Scope

• Add a required checkbox to the second deletion step (permanent deletion modal) for both groups and projects
• Display on GitLab.com and Dedicated instances only (not self-managed)

UI Changes

Add the following checkbox above the action buttons in the permanent deletion modal:

Checkbox text:

• This action permanently deletes this [project/group] and all its data. Your administrator cannot restore it. View data export options.

Behavior:

• Checkbox is unchecked by default
• "Delete permanently" button remains disabled until checkbox is checked
• Link to "View data export options" should open export documentation/functionality

See attached designs for visual reference.

	Before	After - 1st deletion	After - 2nd deletion
Project
Group

Technical Details

• Detect deployment type (GitLab.com/dedicated vs self-managed) to conditionally show checkbox
• Update both project and group deletion modals with identical logic
• Ensure checkbox state properly controls button enable/disable state

Acceptance Criteria

• Checkbox appears on permanent deletion modal for projects on GitLab.com/Dedicated
• Checkbox appears on permanent deletion modal for groups on GitLab.com/Dedicated
• Checkbox does not appear on self-managed instances
• Delete button is disabled until checkbox is checked
• Export options link is functional