Jump to the middle; bold jump arrows; Chicago time; demo hours 6 AM-9 PM

- Jump sheet: Top / Middle / Bottom with the Card fields arrows; the Jump
  button uses the same bold arrows.
- Container timezone defaults to America/Chicago (TZ in Dockerfile/compose).
- Demo worker follows its own business hours (Demo.BusinessHours, default
  06:00-21:00 every day) with the midnight pitstop; the simulated cycle in
  the browser shows the real worker's next run.

web/demo/demo.js

@@ -623,8 +623,10 @@
             const secs = (new Date() - started) / 1000;
             w([]);
             w([[`Cycle Complete in ${secs.toFixed(1)}s.`, 'Gray']]);
-            const next = new Date(Date.now() + 45000);
-            w([[`Next Cycle Scheduled For: ${psStamp(next)}`, 'DarkGray']]);
+            // the real worker's schedule (it sleeps outside the demo's business hours)
+            const ws = await serverGet('/Worker-State.json');
+            const nextText = ws && ws.Status === 'Cooldown' && ws.NextCycle ? ws.NextCycle : psStamp(new Date(Date.now() + 45000));
+            w([[`Next Cycle Scheduled For: ${nextText}`, 'DarkGray']]);
             w([]); w([]);
 
             if (!s.tracked) await ensureOwnRoster();