fix: remove inset background from LogViewer container

LogViewer was using --bg-inset which created a visual mismatch with the
EventFeed timeline panel. Now inherits the parent card's background
(--bg-surface) for consistent appearance in side-by-side layouts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/composites/LogViewer/LogViewer.module.css

@@ -1,7 +1,5 @@
 .container {
   overflow-y: auto;
-  background: var(--bg-inset);
-  border-radius: var(--radius-md);
   padding: 8px 0;
   font-family: var(--font-mono);
 }