Add sources display to import preview for better reference tracking

sbas/templates/sbas/partials/import_preview.html

@@ -30,9 +30,21 @@
               {% if item.payload.e_feedback %}
                 <p><strong>E Feedback:</strong> {{ item.payload.e_feedback|default:''|safe }}</p>
               {% endif %}
+
             </ul>
           </p>
           <p><strong>Feedback:</strong> {{ item.payload.feedback|default:''|safe }}</p>
+          <p>><strong>Sources:</strong>
+            {% if item.payload.sources %}
+              <ul>
+                {% for source in item.payload.sources %}
+                  <li>{{ source }}</li>
+                {% endfor %}
+              </ul>
+            {% else %}
+              None
+            {% endif %}
+            </p>
         {% endif %}
         <p><strong>M2M fields (click to exclude)</strong></p>
         <p class="small text-muted">Green = will be created/attached. Click a value to exclude it (grey).</p>