Diversion planner (nearest airfield / divert-from-here)

[msupino]

Summary

Add a diversion helper: from any point (cursor, selected waypoint, or "my position"), list the nearest airfields with bearing, distance, and ETE/fuel at current performance.

Motivation

In-flight diversion decisions need quick nearest-field info; a planner that surfaces it adds real utility.

Proposed UI

• Right-click / long-press a point → "Nearest airfields" list (name, brg, dist, ETE), click to insert as a diversion leg.
• Optional one-tap "divert from here" that re-routes to the chosen field.

Implementation

• docs/app/interact.js — context action + nearest-field search (reuse airfields dataset); docs/app/core.js — bearing/dist helpers (exist) + strings (en + he).

Acceptance criteria

• Nearest airfields with brg/dist/ETE from a chosen point.
• Insert a diversion leg to a selected field.
• en + he strings.