Time planning: ETD → per-waypoint ETA + last-light / sunset check

[msupino]

Summary

Add a departure time (ETD) and compute ETA at each waypoint (Zulu + local), plus a last-light / sunset check for the route area — critical for VFR.

Motivation

VFR must land before official night. Pilots need ETA per point and a clear warning if the plan runs past last light.

Proposed UI

• ETD input (date + time, local/Zulu toggle) in the Flight Plan modal.
• ETA column per leg/waypoint (cumulative time + ETD).
• A last light readout (sunset + civil twilight) for the destination/route centroid, with a red flag when any ETA is after it.

Data / math

• Sunrise/sunset from lat/lng/date (NOAA solar algorithm — no network needed).
• Civil twilight for "last light".

Implementation

• docs/app/io.js — Flight Plan modal columns + totals; docs/app/core.js — solar calc helper + strings (en + he).
• Persist ETD in localStorage (and optionally route JSON).

Acceptance criteria

• ETA shown per waypoint, updates with ETD / speeds / wind.
• Last-light computed for the route and shown; ETA-after-last-light flagged.
• Local/Zulu toggle.
• en + he strings.