refactor: Remove BackgroundImageDiv component

Component is redundant, move style to CSS class and allows to set the
image via CSS variables

src/components/BackgroundImageDiv.astro

@@ -1,35 +0,0 @@
----
-import { getImage } from 'astro:assets';
-
-interface Props {
-  src: string;
-  width: number;
-  height: number;
-}
-
-const { src, width, height } = Astro.props;
-
-const optimizedBackground = await getImage({
-  src,
-  width,
-  height,
-  format: 'webp',
-});
----
-
-<div id="bg">
-  <slot />
-</div>
-
-<style define:vars={{ bgImage: `url(${optimizedBackground.src})` }}>
-  #bg {
-    background-image: linear-gradient(rgba(0, 0, 0, 0.4), rgba(0, 0, 0, 0.4)),
-      var(--bgImage);
-    background-position: center;
-    background-size: cover;
-    color: var(--prj-bg);
-
-    padding-top: var(--prj-spacing-3);
-    padding-bottom: var(--prj-spacing-3);
-  }
-</style>