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/(jury)/jury/competitions/page.tsx

@@ -2,6 +2,7 @@
 
 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 { Badge } from '@/components/ui/badge'
@@ -20,6 +21,7 @@ import {
 import { formatDateOnly, formatEnumLabel } from '@/lib/utils'
 
 export default function JuryAssignmentsPage() {
+  const router = useRouter()
   const { data: assignments, isLoading } = trpc.assignment.myAssignments.useQuery({})
 
   if (isLoading) {
@@ -58,11 +60,9 @@ export default function JuryAssignmentsPage() {
             Projects assigned to you for evaluation
           </p>
         </div>
-        <Button variant="ghost" size="sm" asChild className="hidden md:inline-flex">
-          <Link href={'/jury' as Route}>
-            <ArrowLeft className="mr-2 h-4 w-4" />
-            Back to Dashboard
-          </Link>
+        <Button variant="ghost" size="sm" onClick={() => router.back()} className="hidden md:inline-flex">
+          <ArrowLeft className="mr-2 h-4 w-4" />
+          Back
         </Button>
       </div>