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/(admin)/admin/dashboard-content.tsx

@@ -116,20 +116,21 @@ function getContextualActions(
 export function DashboardContent({ editionId, sessionName }: DashboardContentProps) {
   const { data, isLoading, error } = trpc.dashboard.getStats.useQuery(
     { editionId },
-    { enabled: !!editionId, retry: 1, refetchInterval: 30_000 }
+    { enabled: !!editionId, refetchInterval: 60_000 }
   )
   const { data: recentEvals } = trpc.dashboard.getRecentEvaluations.useQuery(
     { editionId, limit: 8 },
-    { enabled: !!editionId, refetchInterval: 30_000 }
+    { enabled: !!editionId, refetchInterval: 60_000 }
   )
   const { data: liveActivity } = trpc.dashboard.getRecentActivity.useQuery(
     { limit: 8 },
-    { enabled: !!editionId, refetchInterval: 5_000 }
+    { enabled: !!editionId, refetchInterval: 30_000 }
   )
   const { data: semiFinalistStats } = trpc.dashboard.getSemiFinalistStats.useQuery(
     { editionId },
-    { enabled: !!editionId, refetchInterval: 60_000 }
+    { enabled: !!editionId, refetchInterval: 120_000 }
   )
+  const { data: featureFlags } = trpc.settings.getFeatureFlags.useQuery()
 
   if (isLoading) {
     return <DashboardSkeleton />
@@ -283,6 +284,7 @@ export function DashboardContent({ editionId, sessionName }: DashboardContentPro
                 byAward={semiFinalistStats.byAward}
                 unactivatedProjects={semiFinalistStats.unactivatedProjects}
                 editionId={editionId}
+                reminderThresholdDays={featureFlags?.accountReminderDays}
               />
             </AnimatedCard>
           )}

src/app/(admin)/admin/semi-finalists/page.tsx

@@ -0,0 +1,42 @@
+import type { Metadata } from 'next'
+import { prisma } from '@/lib/prisma'
+import { SemiFinalistsContent } from '@/components/admin/semi-finalists-content'
+
+export const metadata: Metadata = { title: 'Semi-Finalists' }
+export const dynamic = 'force-dynamic'
+
+type PageProps = {
+  searchParams: Promise<{ editionId?: string }>
+}
+
+export default async function SemiFinalistsPage({ searchParams }: PageProps) {
+  const params = await searchParams
+  let editionId = params.editionId || null
+
+  if (!editionId) {
+    const defaultEdition = await prisma.program.findFirst({
+      where: { status: 'ACTIVE' },
+      orderBy: { year: 'desc' },
+      select: { id: true },
+    })
+    editionId = defaultEdition?.id || null
+
+    if (!editionId) {
+      const anyEdition = await prisma.program.findFirst({
+        orderBy: { year: 'desc' },
+        select: { id: true },
+      })
+      editionId = anyEdition?.id || null
+    }
+  }
+
+  if (!editionId) {
+    return (
+      <div className="py-12 text-center text-muted-foreground">
+        No edition found.
+      </div>
+    )
+  }
+
+  return <SemiFinalistsContent editionId={editionId} />
+}