Keep the construction band fixed on desktop

docs/implementation.md

@@ -1,6 +1,6 @@
 # Implementation and maintenance
 
-The supplied 1200 × 900 PDF and its IDML source define the desktop composition. All original design files are preserved under `design/`. The photographic backdrop and construction tape are extracted together to preserve the print export's crop, tint and shadows. The logo and Lumios Marker heading retain their original outlines as SVG artwork; all other content is semantic, selectable HTML in `index.html`.
+The supplied 1200 × 900 PDF and its IDML source define the desktop composition. All original design files are preserved under `design/`. The photographic backdrop and construction tape are extracted together to preserve the print export's crop, tint and shadows. This background stays fixed to the viewport above 1024 px; on smaller screens the background and tape scroll with the page. The logo and Lumios Marker heading retain their original outlines as SVG artwork; all other content is semantic, selectable HTML in `index.html`.
 
 CSS lives in `assets/styles.css`; all colors are CSS custom properties. Layout scales with the design above 1024 px. At smaller sizes the type becomes larger and wraps; at 600 px the bank and PayPal details stack in their original reading order. The mobile background separates the supplied tape from the photograph so that it remains above the logo while the photo fills a tall page. `assets/app.mjs` only enhances the IBAN with clipboard support and an accessible selection fallback. Contact and payment links work without JavaScript.
 

docs/verification.md

@@ -24,3 +24,9 @@ Deployment checks on 2026-09-07:
 - The server-wide inventory contains 13 repositories. Only `showcase/2608_BuB` appears in anonymous repository search; all 12 other repositories are private and reject anonymous API and Git access.
 
 For each published revision, check the `showcase/deploy` status on its Gitea commit and compare the served files with `dist`.
+
+Desktop band follow-up on 2026-09-07:
+
+- The desktop backdrop containing the original band uses fixed positioning above 1024 px. At 1024 px and below, the backdrop and separate band use absolute positioning and scroll normally.
+- Real scrolling at 1200, 1025, 1024 and 390 px confirms the appropriate positioning and no horizontal overflow. Screenshot comparisons of the decorative area remain identical after scrolling on desktop and change on mobile.
+- Inspected the initial and scrolled desktop screenshots against the previously deployed composition; layout and artwork placement are retained.