added header and footer

Co-authored-by: Copilot <copilot@github.com>

src/app/app.ts

@@ -1,9 +1,11 @@
 import { Component } from '@angular/core';
 import { RouterOutlet } from '@angular/router';
+import { SiteHeader } from './site-header/site-header';
+import { SiteFooter } from './site-footer/site-footer';
 
 @Component({
   selector: 'app-root',
-  imports: [RouterOutlet],
+  imports: [RouterOutlet, SiteHeader, SiteFooter],
   templateUrl: './app.html',
   styleUrl: './app.scss'
 })