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>

package.json

@@ -93,7 +93,6 @@
     "@types/papaparse": "^5.3.15",
     "@types/react": "^19.0.2",
     "@types/react-dom": "^19.0.2",
-    "autoprefixer": "^10.4.20",
     "eslint": "^9.17.0",
     "eslint-config-next": "^15.1.0",
     "postcss": "^8.4.49",