Support 'System' theme setting (#91)

src/views/admin.html.ecr

@@ -7,6 +7,14 @@
       <span hidden></span>
     </span>
   </li>
+  <li class="nopointer">
+    <span>Theme</span>
+    <select id="theme-select" class="uk-select uk-align-right uk-width-1-3@m uk-width-1-2">
+      <option>Dark</option>
+      <option>Light</option>
+      <option>System</option>
+    </select>
+  </li>
   <li data-url="<%= base_url %>admin/downloads">Download Manager</li>
 </ul>
 

src/views/layout.html.ecr

@@ -56,7 +56,7 @@
       </div>
     </div>
     <script>
-      setTheme(getTheme());
+      setTheme();
       const base_url = "<%= base_url %>";
     </script>
     <script src="https://cdn.jsdelivr.net/npm/uikit@3.3.1/dist/js/uikit.min.js"></script>

src/views/login.html.ecr

@@ -27,7 +27,7 @@
       </div>
     </div>
     <script>
-      setTheme(getTheme());
+      setTheme();
     </script>
     <script src="https://cdn.jsdelivr.net/npm/uikit@3.3.1/dist/js/uikit.min.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/uikit@3.3.1/dist/js/uikit-icons.min.js"></script>