add(frontend): enable ssr hydration

frontend/src/app/app.config.server.ts

···
 import { provideServerRendering, withRoutes } from '@angular/ssr';
 import { appConfig } from './app.config';
 import { serverRoutes } from './app.routes.server';
+import {provideClientHydration} from '@angular/platform-browser';
 
 const serverConfig: ApplicationConfig = {
   providers: [
-    provideServerRendering(withRoutes(serverRoutes))
+    provideServerRendering(withRoutes(serverRoutes)),
+    provideClientHydration()
   ]
 };