Add cover image detection for audio files in scanner

During scanning, when an audio file is found in a directory that also
contains an image file (jpg/png/gif), the scanner now assigns that image
as the audio file's thumbnail_path. This is common for audiobooks which
have cover.jpg alongside the audio files.

Changes:
- scanner: two-pass walk to collect sibling images, then pair with audio
- CSS: add .row-cover style for audio items with covers
- JS: render audio rows with cover images when thumbnail_path is set

1 files changed, 9 insertions, 0 deletions

diff --git a/web/css/layout.css b/web/css/layout.css
index ca5acd8..006f874 100644
--- a/web/css/layout.css
+++ b/web/css/layout.css
@@ -230,6 +230,15 @@ body {
   white-space: nowrap;
 }
 
+.media-row .row-cover {
+  width: 2.8rem;
+  height: 2.8rem;
+  object-fit: cover;
+  border-radius: var(--radius-sm);
+  flex-shrink: 0;
+  background: var(--bg-elevated);
+}
+
 /* Modal */
 .modal-overlay {
   position: fixed;