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.

README.md

@@ -160,8 +160,9 @@ docker compose up -d --build        # http://localhost:8080
 
 On **Coolify**, create a resource from this repository using the *Dockerfile* (or *Docker
 Compose*) build pack, set the exposed port to **8080**, and attach a domain. The container
-reseeds the simulated fleet on every start and needs no volumes or secrets. Set `TZ` to show
-times in your timezone.
+reseeds the simulated fleet on every start and needs no volumes or secrets. Times are shown in
+`TZ` (default `America/Chicago`); set it to your own timezone. The demo worker runs
+6 AM to 9 PM every day (`Demo.BusinessHours` in the config) and sleeps overnight.
 
 ### Demo (local PowerShell 7)