feat: Create Core Layout Structure

[pestler]

Goal

Generate a primary LayoutComponent to serve as the main UI container for the application.

Implementation Plan

• Generate a new component named LayoutComponent.
• Update layout.component.html to contain placeholders for header, footer, and a <router-outlet>.
• Update app.component.html to only contain the <app-layout> selector.
• Ensure the new component is correctly declared and exported.

[pestler]

Branch: feat/3-core-layout