feat: impersonation system, semi-finalist detail page, tRPC resilience

- Add super-admin impersonation: "Login As" from user list, red banner
  with "Return to Admin", audit logged start/end, nested impersonation
  blocked, onboarding gate skipped during impersonation
- Fix semi-finalist stats: check latest terminal state (not any PASSED),
  use passwordHash OR status=ACTIVE for activation check
- Add /admin/semi-finalists detail page with search, category/status filters
- Add account_reminder_days setting to notifications tab
- Add tRPC resilience: retry on 503/HTML responses, custom fetch detects
  nginx error pages, exponential backoff (2s/4s/8s)
- Reduce dashboard polling intervals (60s stats, 30s activity, 120s semi)

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

src/app/(jury)/layout.tsx

@@ -11,20 +11,22 @@ export default async function JuryLayout({
   children: React.ReactNode
 }) {
   const session = await requireRole('JURY_MEMBER')
+  const isImpersonating = !!session.user.impersonating
 
-  // Check if user has completed onboarding
-  const user = await prisma.user.findUnique({
-    where: { id: session.user.id },
-    select: { onboardingCompletedAt: true },
-  })
+  // Check if user has completed onboarding (skip during impersonation)
+  if (!isImpersonating) {
+    const user = await prisma.user.findUnique({
+      where: { id: session.user.id },
+      select: { onboardingCompletedAt: true },
+    })
 
-  if (!user) {
-    // User was deleted — session is stale, send to login
-    redirect('/login')
-  }
+    if (!user) {
+      redirect('/login')
+    }
 
-  if (!user.onboardingCompletedAt) {
-    redirect('/onboarding')
+    if (!user.onboardingCompletedAt) {
+      redirect('/onboarding')
+    }
   }
 
   return (