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/(observer)/observer/page.tsx

@@ -67,19 +67,24 @@ async function ObserverDashboardContent() {
   return (
     <>
       {/* Observer Notice */}
-      <Card className="border-blue-200 bg-blue-50 dark:border-blue-900 dark:bg-blue-950/30">
-        <CardContent className="flex items-center gap-3 py-4">
-          <Eye className="h-5 w-5 text-blue-600 dark:text-blue-400" />
+      <div className="rounded-lg border-2 border-blue-300 bg-blue-50 px-4 py-3">
+        <div className="flex items-center gap-3">
+          <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-full bg-blue-100">
+            <Eye className="h-4 w-4 text-blue-600" />
+          </div>
           <div>
-            <p className="font-medium text-blue-900 dark:text-blue-100">
-              Observer Mode
-            </p>
-            <p className="text-sm text-blue-700 dark:text-blue-300">
+            <div className="flex items-center gap-2">
+              <p className="font-semibold text-blue-900">Observer Mode</p>
+              <Badge variant="outline" className="border-blue-300 text-blue-700 text-xs">
+                Read-Only
+              </Badge>
+            </div>
+            <p className="text-sm text-blue-700">
               You have read-only access to view platform statistics and reports.
             </p>
           </div>
-        </CardContent>
-      </Card>
+        </div>
+      </div>
 
       {/* Stats Grid */}
       <div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">