feat(admin): implement unified submission and newsletter management

Introduce a centralized system to manage all website form submissions and newsletter subscriptions.
- Add `Submission` and `NewsletterSubscription` models with MongoDB schema validation
- Implement `submissionController` and `newsletterSubscriptionController` for CRUD operations and filtering
- Create a unified admin UI for reviewing submissions across different sources (home, request, contact, partnership, newsletter)
- Add database migration scripts for creating collections and indexes
- Refactor partnership inquiry forms to use a fixed field structure
- Update admin navigation and server CORS settings to support PATCH requests

views/layouts/main.ejs

@@ -1107,9 +1107,15 @@
             <a class="nav-link <%= currentPath === '/admin/contact' ? 'active' : '' %>" href="/admin/contact">Contact
               Us</a>
           </li>
+
+          <li class="nav-item">
+            <a class="nav-link <%= currentPath === '/admin/submissions' ? 'active' : '' %>"
+              href="/admin/submissions">Submission
+            </a>
+          </li>
           
           <li class="nav-item">
-            <a class="nav-link <%= currentPath === '/admin/audit-logs' ? 'active' : '' %>"
+            <a class="nav-link <%= currentPath === '/admin/request-info' ? 'active' : '' %>"
               href="/admin/request-info">Request Info
             </a>
           </li>
@@ -1525,4 +1531,4 @@
   <%- script %>
 </body>
 
-</html>
+</html>