refactor(server, web): standardize theme api response (#4664)

* web: standardize theme api response

* revert makefile change that i didn't mean to commit

web/src/api/open-api/api.ts

@@ -2966,10 +2966,10 @@ export interface ServerStatsResponseDto {
 export interface ServerThemeDto {
     /**
      * 
-     * @type {SystemConfigThemeDto}
+     * @type {string}
      * @memberof ServerThemeDto
      */
-    'theme': SystemConfigThemeDto;
+    'customCss': string;
 }
 /**
  * 

web/src/routes/custom.css/+server.ts

@@ -1,9 +1,7 @@
 import { RequestHandler, text } from '@sveltejs/kit';
 export const GET = (async ({ locals: { api } }) => {
   const {
-    data: {
-      theme: { customCss },
-    },
+    data: { customCss },
   } = await api.serverInfoApi.getTheme();
   return text(customCss, {
     headers: {