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

* web: standardize theme api response

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

server/src/domain/server-info/server-info.dto.ts

@@ -80,9 +80,7 @@ export class ServerMediaTypesResponseDto {
   sidecar!: string[];
 }
 
-export class ServerThemeDto {
-  theme!: SystemConfigThemeDto;
-}
+export class ServerThemeDto extends SystemConfigThemeDto {}
 
 export class ServerConfigDto {
   oauthButtonText!: string;

server/src/domain/server-info/server-info.service.ts

@@ -72,7 +72,7 @@ export class ServerInfoService {
 
   async getTheme() {
     const { theme } = await this.configCore.getConfig();
-    return { theme };
+    return theme;
   }
 
   async getConfig(): Promise<ServerConfigDto> {