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/app/(admin)/admin/juries/[groupId]/page.tsx

@@ -194,10 +194,8 @@ export default function JuryGroupDetailPage({ params }: JuryGroupDetailPageProps
         <Card className="border-dashed">
           <CardContent className="flex flex-col items-center justify-center py-12 text-center">
             <p className="text-muted-foreground">The requested jury group could not be found.</p>
-            <Button asChild className="mt-4" variant="outline">
-              <Link href={'/admin/juries' as Route}>
-                Back to Juries
-              </Link>
+            <Button className="mt-4" variant="outline" onClick={() => router.back()}>
+              Back
             </Button>
           </CardContent>
         </Card>
@@ -212,13 +210,11 @@ export default function JuryGroupDetailPage({ params }: JuryGroupDetailPageProps
         <Button
           variant="ghost"
           size="sm"
-          asChild
           className="mb-2"
+          onClick={() => router.back()}
         >
-          <Link href={'/admin/juries' as Route}>
-            <ArrowLeft className="h-4 w-4 mr-1" />
-            Back to Juries
-          </Link>
+          <ArrowLeft className="h-4 w-4 mr-1" />
+          Back
         </Button>
         <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
           <div>