Add JWT support for authentication handling

Integrate `@auth0/angular-jwt` for Token management. Update `app.config.ts` with `JwtModule` setup and token getter from cookies. Enhance `AuthService` to include token handling, fake login, and JWT validation using `JwtHelperService`. Introduce `JwtClaims` interface for structured token claims.

frontend/src/app/app.config.ts

@@ -1,8 +1,26 @@
 import {ApplicationConfig, provideZoneChangeDetection} from '@angular/core';
 import {provideRouter} from '@angular/router';
+import {JwtHelperService, JwtModule} from '@auth0/angular-jwt';
+import {CookieService} from 'ngx-cookie-service';
 
 import {routes} from './app.routes';
 
+// Function to get the JWT token from cookies
+export function jwtTokenGetter() {
+  const cookieService = new CookieService(document, null);
+  return cookieService.check('jwt') ? cookieService.get('jwt') : null;
+}
+
 export const appConfig: ApplicationConfig = {
-  providers: [provideZoneChangeDetection({eventCoalescing: true}), provideRouter(routes)]
+  providers: [
+    provideZoneChangeDetection({eventCoalescing: true}),
+    provideRouter(routes),
+    { provide: CookieService, useClass: CookieService },
+    { provide: JwtHelperService, useClass: JwtHelperService },
+    { provide: JwtModule, useValue: JwtModule.forRoot({
+      config: {
+        tokenGetter: jwtTokenGetter
+      }
+    })}
+  ]
 };