Restore the turn-antenna button and send the PSTRotator azimuth with one decimal (#126)

* Send the PSTRotator azimuth with one decimal instead of truncating it

setAzimuth cast the azimuth to int, so 145.7 degrees turned the antenna
to 145. It is now rounded to one decimal and formatted with Locale.ROOT,
so a German default locale cannot turn the dot into a comma; a value that
rounds up to 360.0 is sent as 0.0. The loopback test pinned the old
truncation and now expects the decimal.

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

* Bring back the turn-antenna button lost in the Compose migration

The JavaFX station panel had "Turn ant1 to <call>", the only caller of
ChatController.rotateTo; removing JavaFX (fe4215bc) dropped it, so the
antenna could no longer be turned from KST4Contest at all. The Compose
panel gets the button again, enabled when a rotator callback is wired and
the selected station has a finite heading.

Review follow-ups for the decimal azimuth: formatAzimuth refuses NaN and
infinite values and wraps any finite value into [0, 360). The "reached"
check before the SPID retry uses a 1.0 degree tolerance, because the
target now carries a decimal while many controllers report whole degrees.

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

* Keep rotateTo's Javadoc on the method and word the German label as a bearing

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

@@ -32,6 +32,8 @@ Several operators sharing one computer can now use their own callsigns, locators
 
 - **The default login callsign is empty:** if `preferences.xml` has no login callsign, the field now stays empty instead of falling back to a callsign compiled into the program. A newly created profile therefore deliberately starts without credentials.
 
+- **PSTRotator azimuth with one decimal:** the azimuth sent to PSTRotator used to be cut to whole degrees, so a station at 145.7° turned the antenna to 145°. It is now rounded to one decimal, always with a dot as separator.
+
 - **Dark mode per profile:** on the **GUI** tab each operator profile sets under **Design** whether KST4Contest starts light or dark. The entries in the **Windows** menu still switch quickly, but only for the running session. The colour scheme now also covers the update window and the top candidates list.
 
 ### Fixed