fix(web): fix Theme Custom CSS endpoint requiring the user to be logged in as the server admin (#4633)

* fix custom css requiring the user to be the admin and logged in

* move theme api to custom endpoint

* add e2e test

server/src/immich/controllers/server-info.controller.ts

@@ -6,6 +6,7 @@ import {
   ServerMediaTypesResponseDto,
   ServerPingResponse,
   ServerStatsResponseDto,
+  ServerThemeDto,
   ServerVersionResponseDto,
 } from '@app/domain';
 import { Controller, Get } from '@nestjs/common';
@@ -43,6 +44,12 @@ export class ServerInfoController {
     return this.service.getFeatures();
   }
 
+  @PublicRoute()
+  @Get('theme')
+  getTheme(): Promise<ServerThemeDto> {
+    return this.service.getTheme();
+  }
+
   @PublicRoute()
   @Get('config')
   getServerConfig(): Promise<ServerConfigDto> {