Import UI: show per-file rejection reasons in the processing window (#804)

CubeComming had to dig through app.log to learn WHY a file failed ("integrity
check failed: Duration mismatch ..."). The reason was already returned in the
singles/process `errors` array and carried on the queue entry — the window just
showed "Failed" with no detail.

Now each failed file's reason renders under its row (red, left-bordered, with a
title tooltip for the full text). Pure presentation of data already present; no
API change. Vite build clean.

webui/src/routes/import/-ui/import-page.module.css

@@ -769,6 +769,29 @@
   margin-top: 2px;
 }
 
+/* Per-file rejection reasons (quarantine / integrity / match failures) so the
+   "why" shows in the window, not just in the log (#804). */
+.importPageQueueErrors {
+  list-style: none;
+  margin: 4px 0 0;
+  padding: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.importPageQueueErrors li {
+  font-size: 11px;
+  line-height: 1.35;
+  color: #ff6b6b;
+  background: rgba(255, 107, 107, 0.08);
+  border-left: 2px solid rgba(255, 107, 107, 0.5);
+  padding: 2px 6px;
+  border-radius: 3px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
 .importPageQueueProgress {
   width: 120px;
   flex-shrink: 0;

webui/src/routes/import/-ui/import-page.tsx

@@ -160,6 +160,15 @@ function ImportQueueItem({ entry }: { entry: ImportQueueEntry }) {
       <div className={styles.importPageQueueInfo}>
         <div className={styles.importPageQueueName}>{entry.label}</div>
         <div className={styles.importPageQueueDetail}>{entry.sublabel}</div>
+        {entry.errors.length > 0 && (
+          <ul className={styles.importPageQueueErrors}>
+            {entry.errors.map((err, i) => (
+              <li key={i} title={err}>
+                {err}
+              </li>
+            ))}
+          </ul>
+        )}
       </div>
       <div className={styles.importPageQueueProgress}>
         <div className={styles.importPageQueueBar}>