fix: replace position: sticky with absolute for capture range label

The .timeline-capture-move span uses position: sticky; left: 50% to
keep the time range label (e.g. "24h", "48h") visible. However,
sticky for horizontal scroll doesn't work reliably here because the
span is deeply nested inside multiple position: absolute parents
(.timeline-capture-overlay -> .timeline-capture-selection ->
.timeline-capture-move). The horizontal sticky behavior never kicks
in, so the label scrolls with the content and can drift off-screen to
the left when the user scrolls right to capture a later part of the
timeline.

Fix: use position: absolute; left: 50%; top: 15px; transform: translateX(-50%)
instead. This centers the label within the selection box itself. Since the
selection box scrolls normally with the content, the label stays centered
within the selection at all scroll positions in both directions.

Co-authored-by: Openclaw <openclaw@local>

Author: Enter-tainer

src/components/Dashboard.css

@@ -571,7 +571,7 @@
 }
 
 .timeline-capture-move span {
-  position: sticky;
+  position: absolute;
   top: 15px;
   left: 50%;
   display: inline-flex;