✨ Improve cache handling.

And make the devenv http server behave similar to a production
environment (related to cache handling).

frontend/resources/templates/index.mustache

@@ -16,7 +16,9 @@
       window.uxboxTranslations = JSON.parse({{& translations }});
       window.uxboxThemes = {{& themes }};
     </script>
-    <script src="/js/shared.js?ts={{& ts }}"></script>
-    <script src="/js/main.js?ts={{& ts }}"></script>
+    {{# manifest}}
+      <script src="{{& shared}}"></script>
+      <script src="{{& main}}"></script>
+    {{/manifest}}
   </body>
 </html>