UI/UX audit fixes: clickable pipelines, broken links, isActive locking

- Make pipeline cards clickable on list page (navigate to detail view)
- Fix broken nav link: applicant /messages → /mentor
- Fix broken nav link: mentor /messages → /projects
- Add isActive field locking to all 7 wizard sections (intake, main-track,
  filtering, assignment, awards, live-finals, notifications)
- Add minLoad ≤ maxLoad cross-field validation in assignment section
- Add duplicate stage slug detection in main track section
- Add active pipeline warning banners in intake and main track sections

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/(mentor)/mentor/page.tsx

@@ -189,7 +189,7 @@ export default function MentorDashboard() {
       {/* Quick Actions */}
       <div className="flex flex-wrap gap-2">
         <Button variant="outline" size="sm" asChild>
-          <Link href={'/mentor/messages' as Route}>
+          <Link href={'/mentor/projects' as Route}>
             <Mail className="mr-2 h-4 w-4" />
             Messages
           </Link>