Update CSS imports and Dockerfile for consistent styles handling

- Enforced `!important` for `--color-background` in `variables.css`.
- Centralized CSS imports in `Layout.astro` for cleaner markup.
- Adjusted Dockerfile to ensure CSS variables are copied to `public/styles`.
- Refined fallback handling in `index.css` for `background-color`.

.idea/Gallus_Pub.iml

@@ -8,6 +8,5 @@
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
-    <orderEntry type="library" name="font-awesome" level="application" />
   </component>
 </module>