feat: integrate Tailwind CSS and implement dark mode functionality

- Added Tailwind CSS dependencies and configured PostCSS.
- Updated app component to wrap router outlet with a styled div for dark mode support.
- Modified routing to include a default route and added auth guards.
- Implemented dark mode toggle functionality in content component.
- Enhanced login component with improved styling and lifecycle management.
- Created items component with basic structure and routing.
- Added global styles for body and dark mode variants.
- Updated tests for new items component.

Web/src/app/content/content.ts

@@ -1,16 +1,18 @@
 import { JsonPipe } from '@angular/common';
-import { HttpClient, HttpHeaders } from '@angular/common/http';
-import { Component, isDevMode, signal } from '@angular/core';
+import { HttpClient } from '@angular/common/http';
+import { Component, OnInit, signal } from '@angular/core';
 import { OAuthService } from 'angular-oauth2-oidc';
 import { AppConfigService } from '../services/config.service';
+import { RouterLink, RouterOutlet } from "@angular/router";
+import { setTheme } from '../app';
 
 @Component({
   selector: 'app-content',
-  imports: [JsonPipe],
+  imports: [JsonPipe, RouterOutlet, RouterLink],
   templateUrl: './content.html',
   styleUrl: './content.scss'
 })
-export class Content {
+export class Content implements OnInit {
   data = signal({});
 
   constructor(httpClient: HttpClient, readonly as: OAuthService, readonly cs: AppConfigService) {
@@ -19,4 +21,16 @@ export class Content {
         this.data.set(data);
       });
   }
+
+  ngOnInit(): void {
+    setTheme();
+  }
+
+  toggleMode() {
+    sessionStorage.getItem('isDarkMode') === 'true' ?
+      sessionStorage.setItem('isDarkMode', 'false') : sessionStorage.setItem('isDarkMode', 'true');
+    setTheme();
+  }
 }
+
+