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/members/[id]/page.tsx

@@ -224,11 +224,9 @@ export default function MemberDetailPage() {
             {error?.message || 'The member you\'re looking for does not exist.'}
           </AlertDescription>
         </Alert>
-        <Button asChild>
-          <Link href="/admin/members">
-            <ArrowLeft className="mr-2 h-4 w-4" />
-            Back to Members
-          </Link>
+        <Button onClick={() => router.back()}>
+          <ArrowLeft className="mr-2 h-4 w-4" />
+          Back
         </Button>
       </div>
     )
@@ -239,11 +237,9 @@ export default function MemberDetailPage() {
   return (
     <div className="space-y-6">
       {/* Back nav */}
-      <Button variant="ghost" asChild className="-ml-4">
-        <Link href="/admin/members">
-          <ArrowLeft className="mr-2 h-4 w-4" />
-          Back to Members
-        </Link>
+      <Button variant="ghost" className="-ml-4" onClick={() => router.back()}>
+        <ArrowLeft className="mr-2 h-4 w-4" />
+        Back
       </Button>
 
       {/* Header Hero */}

src/app/(admin)/admin/members/invite/page.tsx

@@ -2,6 +2,7 @@
 
 import { useState, useCallback, useMemo } from 'react'
 import Link from 'next/link'
+import { useRouter } from 'next/navigation'
 import Papa from 'papaparse'
 import { trpc } from '@/lib/trpc/client'
 import { Button } from '@/components/ui/button'
@@ -257,6 +258,7 @@ function TagPicker({
 }
 
 export default function MemberInvitePage() {
+  const router = useRouter()
   const [step, setStep] = useState<Step>('input')
   const [inputMethod, setInputMethod] = useState<'manual' | 'csv'>('manual')
   const [rows, setRows] = useState<MemberRow[]>([createEmptyRow()])
@@ -1044,11 +1046,9 @@ export default function MemberInvitePage() {
   return (
     <div className="space-y-6">
       <div className="flex items-center gap-4">
-        <Button variant="ghost" asChild className="-ml-4">
-          <Link href="/admin/members">
-            <ArrowLeft className="mr-2 h-4 w-4" />
-            Back to Members
-          </Link>
+        <Button variant="ghost" className="-ml-4" onClick={() => router.back()}>
+          <ArrowLeft className="mr-2 h-4 w-4" />
+          Back
         </Button>
       </div>