update /user/site-settings.html template (initial 'danger zone').

This commit establishes the 'danger zone' in the site's settings page. This will
need to be added to over time. This commit set-ups the 're-populate search DB'
feature but the back-end is not yet implemented.

templates/user/site-settings.html

@@ -267,5 +267,37 @@
             Save Snippet
 	</button>
     </form>
+
+    <hr>
+    
+    {% if roles.administrator %}
+    <div class="be-danger-zone">
+        <h2 class="be-warning">Danger Zone</h2>
+        <p class="be-warning">
+            <strong>Be careful here. You can break the website and lose data.</strong>
+        </p>
+        <form class="be-gui-form"
+              action="/danger/repopulate-search-db"
+              method="post">
+            <input required
+                   type="hidden"
+                   name="AUTHENTICITY-TOKEN"
+                   value="{{token}}">
+            <p class="be-gui-form-hint">
+                If you find Archive Entry thumbnails are no longer loading or
+                you're seeing '404' errors when clicking throught to an Archive
+                Entry, click the button below to re-sync. this website's
+                database with the 'Search Service' database. 
+            </p>
+            <button class="be-gui-button danger"
+		    title="Repopulate the Meilisearch database."
+		    type="submit">
+	        <img alt="Save nav. menu setting for{{db-data.title}}"
+		     src="/images/icons/error-refresh.png">
+                Re-populate Search Database
+	    </button>
+        </form>
+    </div>
+    {% endif %}
 </main>
 {% endblock %}