feat: Add Banner component to file generator output

- Integrated `Banner.astro` into generated file layout for consistent use across components.

backend/src/services/file-generator.service.ts

@@ -43,6 +43,7 @@ export class FileGeneratorService {
 
     return `---
 import Layout from "../components/Layout.astro";
+import Banner from "../components/Banner.astro";
 import Hero from "../components/Hero.astro";
 import Welcome from "../components/Welcome.astro";
 import EventsGrid from "../components/EventsGrid.astro";
@@ -61,6 +62,7 @@ ${imagesCode}
 ---
 
 <Layout>
+\t<Banner />
 \t<Hero id="hero" />
 \t<Welcome id="welcome" />
 \t<EventsGrid id="events" events={events} />