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/programs/[id]/edit/page.tsx

@@ -134,11 +134,9 @@ export default function EditProgramPage() {
     <div className="space-y-6">
       <div className="flex items-center justify-between">
         <div className="flex items-center gap-4">
-          <Link href={`/admin/programs/${id}`}>
-            <Button variant="ghost" size="icon">
-              <ArrowLeft className="h-4 w-4" />
-            </Button>
-          </Link>
+          <Button variant="ghost" size="icon" onClick={() => router.back()}>
+            <ArrowLeft className="h-4 w-4" />
+          </Button>
           <div>
             <h1 className="text-2xl font-bold">Edit Program</h1>
             <p className="text-muted-foreground">

src/app/(admin)/admin/programs/[id]/mentorship/page.tsx

@@ -1,8 +1,7 @@
 'use client'
 
 import { useState } from 'react'
-import { useParams } from 'next/navigation'
-import Link from 'next/link'
+import { useParams, useRouter } from 'next/navigation'
 import { trpc } from '@/lib/trpc/client'
 import {
   Card,
@@ -68,6 +67,7 @@ const defaultMilestoneForm: MilestoneFormData = {
 
 export default function MentorshipMilestonesPage() {
   const params = useParams()
+  const router = useRouter()
   const programId = params.id as string
 
   const [dialogOpen, setDialogOpen] = useState(false)
@@ -184,11 +184,9 @@ export default function MentorshipMilestonesPage() {
     <div className="space-y-6">
       {/* Header */}
       <div className="flex items-center gap-4">
-        <Button variant="ghost" asChild className="-ml-4">
-          <Link href="/admin/programs">
-            <ArrowLeft className="mr-2 h-4 w-4" />
-            Back to Programs
-          </Link>
+        <Button variant="ghost" className="-ml-4" onClick={() => router.back()}>
+          <ArrowLeft className="mr-2 h-4 w-4" />
+          Back
         </Button>
       </div>
 

src/app/(admin)/admin/programs/new/page.tsx

@@ -56,11 +56,9 @@ export default function NewProgramPage() {
   return (
     <div className="space-y-6">
       <div className="flex items-center gap-4">
-        <Link href="/admin/programs">
-          <Button variant="ghost" size="icon">
-            <ArrowLeft className="h-4 w-4" />
-          </Button>
-        </Link>
+        <Button variant="ghost" size="icon" onClick={() => router.back()}>
+          <ArrowLeft className="h-4 w-4" />
+        </Button>
         <div>
           <h1 className="text-2xl font-bold">Create Program</h1>
           <p className="text-muted-foreground">