Platform review round 2: audit logging migration, nav unification, DB indexes, and UI polish

- Migrate ~41 inline audit log calls to shared logAudit() utility across all routers
- Add transaction-aware prisma parameter to logAudit() for atomic operations
- Unify jury/mentor/observer navigation into shared RoleNav component
- Add composite DB indexes (Evaluation, GracePeriod, AuditLog) for query performance
- Fix profile page: consolidate dual save buttons, proper useEffect initialization
- Enhance auth error page with MOPC branding and navigation
- Improve observer dashboard with prominent read-only badge
- Fix DI-3: fetch projects before bulk status update for accurate notifications
- Remove unused aiBoost field from smart-assignment scoring
- Add shared image-upload utility and structured logger module

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

src/app/(auth)/error/page.tsx

@@ -4,6 +4,7 @@ import { useSearchParams } from 'next/navigation'
 import Link from 'next/link'
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
 import { Button } from '@/components/ui/button'
+import { Logo } from '@/components/shared/logo'
 import { AlertCircle } from 'lucide-react'
 
 const errorMessages: Record<string, string> = {
@@ -21,16 +22,22 @@ export default function AuthErrorPage() {
   return (
     <Card className="w-full max-w-md">
       <CardHeader className="text-center">
-        <div className="mx-auto mb-4 flex h-12 w-12 items-center justify-center rounded-full bg-destructive/10">
+        <div className="mx-auto mb-4">
+          <Logo variant="small" />
+        </div>
+        <div className="mx-auto mb-2 flex h-12 w-12 items-center justify-center rounded-full bg-destructive/10">
           <AlertCircle className="h-6 w-6 text-destructive" />
         </div>
         <CardTitle className="text-xl">Authentication Error</CardTitle>
       </CardHeader>
       <CardContent className="space-y-4 text-center">
         <p className="text-muted-foreground">{message}</p>
-        <div className="border-t pt-4">
+        <div className="flex gap-3 justify-center border-t pt-4">
           <Button asChild>
-            <Link href="/login">Try again</Link>
+            <Link href="/login">Return to Login</Link>
+          </Button>
+          <Button variant="outline" asChild>
+            <Link href="/">Home</Link>
           </Button>
         </div>
       </CardContent>