Show * mark when list editor has unsaved changes

Add a red asterisk in the top-right of the dashboard header (and
prefix the document title with *) whenever the dirty flag is set,
so the user can tell at a glance that the music/image list hasn't
been saved yet. The indicator is driven by markDirty/markClean so
it follows the existing tracking.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

public/styles.css

@@ -545,3 +545,15 @@ body.siteBody.centerLayout {
 }
 .packCard.pickable { cursor: pointer; }
 .packCard.pickable:hover { border-color: var(--accent); }
+
+/* 저장 안 됨 표시 (목록 편집기) */
+.dirtyMark {
+  font-size: 36px;
+  font-weight: 700;
+  color: var(--danger, #f85149);
+  line-height: 1;
+  margin-left: auto;
+  align-self: flex-start;
+  padding: 4px 8px;
+  user-select: none;
+}