v1.8.3 - Earth Curvature LOS Fixes and Config Cleanup

This release fixes the LOS tool so it no longer ignores Earth curvature, and it cleans up the related configuration and documentation.

LOS Fixes

• Fixed issue #53: the LOS tool now accounts for Earth curvature instead of using a purely straight terrain-versus-line check
• Applied the same curvature-aware LOS math to both the frontend realtime LOS path and the backend /los fallback so live interaction and server responses stay consistent
• Updated LOS blockage and elevation-profile calculations to use curvature-adjusted terrain samples, which can now correctly mark longer paths as blocked where the previous LOS tool showed clear

New LOS Environment Controls

• Added LOS_CURVATURE_ENABLED
• Added LOS_CURVATURE_FACTOR

Defaults when unset:

• LOS_CURVATURE_ENABLED=true
• LOS_CURVATURE_FACTOR=1.333333

Config and Runtime Fixes

• Fixed docker-compose.yaml so all LOS-related environment variables are actually passed into the container:
  • LOS_ELEVATION_URL
  • LOS_ELEVATION_PROXY_URL
  • LOS_SAMPLE_MIN
  • LOS_SAMPLE_MAX
  • LOS_SAMPLE_STEP_METERS
  • ELEVATION_CACHE_TTL
  • LOS_CURVATURE_ENABLED
  • LOS_CURVATURE_FACTOR
  • LOS_PEAKS_MAX

Docs

• Updated .env.example with the new LOS curvature environment variables
• Clarified MQTT authentication docs for meshcore-mqtt-broker: the live map normally uses a broker SUBSCRIBER_N username/password pair, not node-style signed publisher auth
• Updated version, docs, and changelog for v1.8.3

Validation

• pytest -q → 92 passed, 2 skipped
• node --check backend/static/app.js
• python3 -m py_compile backend/*.py