Replaces the one-time UTC-to-local formatting with a per-second
countdown (HH:MM:SS, or MM:SS under an hour) that fits the dark
cockpit theme's instrument-panel feel, falling back to "due now" once
the target passes instead of showing a negative duration.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Exposes the scheduler's next_tick in the topbar via a safe Jinja
helper (falls back to nothing if the scheduler isn't running yet),
and converts the server-rendered UTC timestamp to the visitor's local
time client-side so it reads correctly regardless of timezone.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>