Side panel: scrollbar matches the APDU list's width

- the side panel had no scrollbar rule of its own, so it fell back to the
  global 6px default while the APDU list uses 12px; the two now share one
  rule (width 12px, thumb radius 6px = half the bar), so they cannot drift
  apart again — the other panes keep the thin global bar
- Node test pins the shared rule (and the 6px global default)
- SW cache simtrace-analyser-v74 (cosmetic, no version bump)

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v73';
+const CACHE = 'simtrace-analyser-v74';
 
 const PRECACHE = [
     'index.html',