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/admin/submissions/index.ejs

@@ -0,0 +1,137 @@
+<div class="container my-4">
+  <div class="d-flex justify-content-between align-items-center mb-4">
+    <div>
+      <h1 class="h3 mb-0" style="color: var(--primary-dark)"><%= title %></h1>
+      <p class="text-muted mb-0"><%= subtitle %></p>
+    </div>
+  </div>
+
+  <div class="card border-0 shadow-sm">
+    <div class="card-header bg-white border-bottom">
+      <ul class="nav nav-tabs card-header-tabs" role="tablist">
+        <% sources.forEach((source) => { %>
+          <li class="nav-item" role="presentation">
+            <button
+              class="nav-link <%= activeSource === source ? 'active' : '' %>"
+              type="button"
+              role="tab"
+              data-submission-tab="<%= source %>"
+            >
+              <%= sourceLabels[source] %>
+              <small class="text-muted">(<%= sourceUrls[source] %>)</small>
+            </button>
+          </li>
+        <% }) %>
+      </ul>
+    </div>
+
+    <div class="card-body">
+      <div class="row g-3 align-items-end mb-4">
+        <div class="col-md-3">
+          <label class="form-label small text-muted">Search</label>
+          <input type="search" class="form-control" id="submissionSearch" placeholder="Name, email, phone">
+        </div>
+        <div class="col-md-2">
+          <label class="form-label small text-muted">Status</label>
+          <select class="form-select" id="submissionStatus">
+            <option value="">All statuses</option>
+            <% statuses.forEach((status) => { %>
+              <option value="<%= status %>"><%= status.replace("_", " ") %></option>
+            <% }) %>
+          </select>
+        </div>
+        <div class="col-md-2">
+          <label class="form-label small text-muted">Start Date</label>
+          <input type="date" class="form-control" id="submissionStartDate">
+        </div>
+        <div class="col-md-2">
+          <label class="form-label small text-muted">End Date</label>
+          <input type="date" class="form-control" id="submissionEndDate">
+        </div>
+        <div class="col-md-1">
+          <label class="form-label small text-muted">Show</label>
+          <select class="form-select" id="submissionPageSize">
+            <option value="10">10</option>
+            <option value="20" selected>20</option>
+            <option value="50">50</option>
+            <option value="100">100</option>
+          </select>
+        </div>
+        <div class="col-md-2 d-flex gap-2">
+          <button type="button" class="btn btn-primary flex-fill" id="submissionApplyFilters">
+            <i class="fas fa-filter me-1"></i>Filter
+          </button>
+          <button type="button" class="btn btn-outline-secondary" id="submissionClearFilters">
+            Clear
+          </button>
+        </div>
+      </div>
+
+      <div class="table-responsive">
+        <table class="table table-hover align-middle">
+          <thead class="table-light">
+            <tr>
+              <th>Date</th>
+              <th data-submission-name-column>Name</th>
+              <th data-submission-email-column>Email</th>
+              <th data-submission-phone-column>Phone</th>
+              <th>Status</th>
+              <th class="text-end">Actions</th>
+            </tr>
+          </thead>
+          <tbody id="submissionRows">
+            <tr>
+              <td colspan="6" class="text-center text-muted py-5">Loading submissions...</td>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+
+      <div class="d-flex justify-content-between align-items-center mt-3">
+        <small class="text-muted" id="submissionPaginationSummary"></small>
+        <div class="btn-group">
+          <button type="button" class="btn btn-outline-secondary btn-sm" id="submissionPrevPage">Previous</button>
+          <button type="button" class="btn btn-outline-secondary btn-sm" id="submissionNextPage">Next</button>
+        </div>
+      </div>
+    </div>
+  </div>
+</div>
+
+<%- include("partials/submission-modal", { statuses }) %>
+
+<script type="application/json" id="submissionManagerConfigJson"><%- JSON.stringify({
+  sources,
+  statuses,
+  statusesBySource: {
+    newsletter: newsletterStatuses,
+  },
+  initialSource: activeSource,
+  urlTabParam: true,
+  hiddenFieldsBySource: {
+    partnership: {
+      email: true,
+      phone: true,
+    },
+    newsletter: {
+      name: true,
+      phone: true,
+    },
+  },
+  apiBySource: {
+    newsletter: {
+      list: "/admin/newsletter-subscriptions/data",
+      detail: "/admin/newsletter-subscriptions",
+      update: "/admin/newsletter-subscriptions",
+    },
+  },
+  itemLabelBySource: {
+    newsletter: "subscriptions",
+  },
+}) %></script>
+<script>
+  window.submissionManagerConfig = JSON.parse(
+    document.getElementById("submissionManagerConfigJson").textContent || "{}",
+  );
+</script>
+<%- include("partials/submission-manager-script") %>