For each (rover cell, fixed station) pair, sample SRTM along the
great-circle path and add a per-link dB bonus proportional to the
rover's elevation above the highest intermediate terrain. Rover spots
on hilltops with clear sight to multiple stations now rise to the top.
Also vendor Leaflet's layers control PNGs and copy them under
priv/static/assets/css/images/ on build so /rover stops 404'ing on
layers-2x.png.
- Extract scoring logic to Microwaveprop.Rover.Coverage for testability
- Two-phase computation: fast pass (distance + propagation) for all grids,
then SRTM terrain analysis for top 20 candidates only
- Cap search radius to 300 km to keep candidate count reasonable
- Run terrain analysis in Task with rescue/fallback for resilience
- Background Task doesn't block LiveView process
- 5 tests covering: ranked results, empty inputs, station details,
band range differences, field presence
