Path analysis: own ground height ASL and highest point of the remote locator square (#133)

* Path analysis: own ground height ASL and highest point of the remote square

Two new settings in the path-analysis section of the Station tab:

- Own ground height ASL (stn_pathAnalysisOwnHeightAslMeters). Empty keeps
  the elevation model value at the own locator centre; a value from -500 to
  9000 m replaces the elevation of the first profile sample. The antenna
  height AGL is still added on top. The field commits on Enter or focus
  loss into the settings draft and reports a refused entry; it keeps the
  operator's spelling while that names the drafted number, because the
  draft is Compose state and would otherwise swap "25" for "25.0" under
  the cursor right after Enter.
- Target station on the highest point of its locator square
  (stn_pathAnalysisDxHighestPointInSquare, on by default). The remote square
  is sampled on a 5 x 5 grid of cell centres in one batched request against
  the Open-Meteo provider, the highest sample becomes the path end with its
  position and elevation. LocatorHighestPointResolver caches the result per
  locator for the session and backs off five minutes after a failure
  (failure list pruned and bounded); the analysis then falls back to the
  square centre and that result is not kept.

Both settings are drafted like the other path-analysis settings and take
effect with Apply/Close or Save; the reachability service reads the stored
values only.

The lookup runs on the reachability thread only. Building a request peeks
the resolver cache without blocking, so a cached square moves the endpoint
right away. The calculation key now includes the own height and the remote
ground elevation at full precision, and the switch, so changing either
recalculates.

Also assign the result of sanitizeEffectiveEarthRadiusFactor in the
PathAnalysisRequest constructor; it was called and dropped. No behaviour
change: the sanitizer is the identity for valid factors, and the analysis
service sanitizes again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Document own ground height and highest-point setting of the path analysis

Changelog v1.50 (New), configuration and features pages in English and
German, and the terrain section of PROJECT_CONTEXT.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

github_docs/en-Changelog.md

@@ -28,6 +28,8 @@ Several operators sharing one computer can now use their own callsigns, locators
 
 - **Windows installer:** next to the portable ZIP package, stable releases now also ship an MSI installer for Windows (`KST4Contest-v<version>-windows-x64.msi`). It installs KST4Contest for the current user account without administrator rights, adds a Start menu entry and a desktop shortcut, and replaces the existing installation on an update. Settings and database stay under `%USERPROFILE%\.praktiKST` and are shared with a portable copy. This implements the first stage of [Issue #61](https://github.com/praktimarc/kst4contest/issues/61).
 
+- **Own site height and highest point of the remote square in the path analysis:** the **Station** tab has two new settings in its path-analysis section. **Own ground height ASL, metres** replaces the elevation-model value at the own locator centre by the height of the actual site; left empty, the elevation model decides as before. **Target station on the highest point of its locator square**, on by default, ends the path at the highest of 25 sampled points of the remote locator square instead of at its centre, because contest stations usually operate from the high ground of their square. The lookup costs one additional request to the elevation service per remote square and session; if it fails, the analysis uses the square centre as before.
+
 ### Changed
 
 - **The terrain profile cache is separate:** computed terrain profiles now live in their own shared file `terrainprofilecache.db` and are stored per owner. Previously the whole cache was dropped whenever the callsign or locator changed, which would have discarded every computed profile on each profile switch.