docs: add JSDoc comments to AuthGuard functions and move to dedicated folder

frontend/src/app/app.routes.ts

@@ -3,7 +3,7 @@ import { ImprintComponent } from './shared/components/legal-information/imprint/
 import { PrivacyPolicyComponent } from './shared/components/legal-information/privacy-policy/privacy-policy.component';
 import { HomeComponent } from './components/home/home.component';
 import { AuthComponent } from './components/auth/auth.component';
-import { AuthGuard } from './auth.guard';
+import { AuthGuard } from './guards/auth.guard';
 
 export const routes: Routes = [
   { path: '', component: AuthComponent },

frontend/src/app/auth.guard.spec.ts

@@ -1,17 +0,0 @@
-import { TestBed } from '@angular/core/testing';
-import { CanActivateFn } from '@angular/router';
-
-import { authGuard } from './auth.guard';
-
-describe('authGuard', () => {
-  const executeGuard: CanActivateFn = (...guardParameters) => 
-      TestBed.runInInjectionContext(() => authGuard(...guardParameters));
-
-  beforeEach(() => {
-    TestBed.configureTestingModule({});
-  });
-
-  it('should be created', () => {
-    expect(executeGuard).toBeTruthy();
-  });
-});

frontend/src/app/guards/auth.guard.ts

@@ -2,7 +2,7 @@ import { Injectable } from '@angular/core';
 import { Router } from '@angular/router';
 import { Observable, of } from 'rxjs';
 import { map, catchError } from 'rxjs/operators';
-import { AuthService } from './services/auth.service';
+import { AuthService } from '../services/auth.service';
 
 @Injectable({
   providedIn: 'root',
@@ -10,6 +10,12 @@ import { AuthService } from './services/auth.service';
 export class AuthGuard {
   constructor(private authService: AuthService, private router: Router) {}
 
+  /**
+   * Determines if the route can be activated by checking if the user is authenticated.
+   *
+   * @returns An Observable, Promise, or boolean indicating whether the route can be activated.
+   *          If the user is authenticated, returns true; otherwise, navigates to the root path and returns false.
+   */
   canActivate(): Observable<boolean> | Promise<boolean> | boolean {
     return this.authService.checkAuthUser().pipe(
       map((isAuthenticated) => {