feat: router.back() navigation, read-only evaluation view, auth audit logging

- Convert all Back buttons platform-wide (38 files) to use router.back()
  for natural browser-back behavior regardless of entry point
- Add read-only view for submitted evaluations in closed rounds with
  blue banner, disabled inputs, and contextual back navigation
- Add auth audit logs: MAGIC_LINK_SENT, PASSWORD_RESET_LINK_CLICKED,
  PASSWORD_RESET_LINK_EXPIRED, PASSWORD_RESET_LINK_INVALID
- Learning Hub links navigate in same window for all roles
- Update settings descriptions to reflect all-user scope

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

src/components/admin/semi-finalists-content.tsx

@@ -3,6 +3,7 @@
 import { useState, useMemo } from 'react'
 import Link from 'next/link'
 import type { Route } from 'next'
+import { useRouter } from 'next/navigation'
 import { trpc } from '@/lib/trpc/client'
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
 import { Input } from '@/components/ui/input'
@@ -55,6 +56,7 @@ type SemiFinalistsContentProps = {
 }
 
 export function SemiFinalistsContent({ editionId }: SemiFinalistsContentProps) {
+  const router = useRouter()
   const { data, isLoading } = trpc.dashboard.getSemiFinalistDetail.useQuery(
     { editionId },
     { enabled: !!editionId }
@@ -116,11 +118,9 @@ export function SemiFinalistsContent({ editionId }: SemiFinalistsContentProps) {
       {/* Header */}
       <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
         <div className="flex items-center gap-3">
-          <Link href={'/admin' as Route}>
-            <Button variant="ghost" size="icon" className="h-8 w-8">
-              <ArrowLeft className="h-4 w-4" />
-            </Button>
-          </Link>
+          <Button variant="ghost" size="icon" className="h-8 w-8" onClick={() => router.back()}>
+            <ArrowLeft className="h-4 w-4" />
+          </Button>
           <div>
             <h1 className="text-xl font-bold tracking-tight md:text-2xl">
               Semi-Finalists