fix(ui): serve SPA bundle from root, add cache-busting query, expose files API and include default CSS manager styles

ts_web/elements/opencdn-mainpage.ts

@@ -4,6 +4,7 @@ import {
   html,
   customElement,
   type TemplateResult,
+  cssManager,
   css,
   state,
 } from '@design.estate/dees-element';
@@ -31,6 +32,7 @@ export class OpencdnMainpage extends DeesElement {
 
   // Shadcn-like color palette
   public static styles = [
+    cssManager.defaultStyles,
     css`
       :host {
         --background: #09090b;