Fix UDP listener defects (#115) (#122)

* fix: let ReadUDPbyUCXMessageThread own its DatagramSocket so interrupt() closes it (#115)

The field `socket` was a java.net.Socket that was never assigned; the real
DatagramSocket lived in a local variable of run(). interrupt() therefore
closed nothing and terminateConnection() would have thrown a
NullPointerException. The receive loop kept running in two-second timeout
steps until the user-disconnect flag was set.

The field is now the DatagramSocket, run() binds it when no pre-bound socket
was handed in, the loop ends on the interrupt flag or a closed socket, and
both interrupt() and terminateConnection() are null-safe. A package-private
constructor accepts a pre-bound socket so loopback tests can listen on an
ephemeral port; the public constructor used by ChatController is unchanged.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix: stop ReadUDPbyUCXMessageThread truncating datagrams after a short packet (#115)

A DatagramPacket keeps the length of the last datagram it received, so a
long RadioInfo packet following a short one was cut to the short one's
length and failed to parse. The length is reset to the buffer size before
every receive, the same way ReadUDPByWintestThread does it. The loopback
test sends a short and then a long packet on port 0 and checks that both
frequencies arrive.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix: give PstRotatorClient's port constructor a callback, decode AirScout as UTF-8 (#115)

The explicit-port constructor left the thread-status callback null, so
start() and the first received packet threw an NPE; the default
constructor now delegates to it. The AirScout listener decoded replies
with the platform charset although the inquirer sends UTF-8.
PROJECT_CONTEXT listed PSTRotator as TCP; the client speaks UDP.

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

* fix: decode UCX datagrams as UTF-8 and tighten the interrupt test (#115)

Review follow-up. UCXLog sends UTF-8 XML, but the listener decoded with
the platform charset before handing a String to the parser, so the XML
header's encoding was ignored. The port-in-use fallback now sets its
receive timeout before the first receive(). The interrupt test waits
1 s, below the 2 s receive timeout, so it fails if interrupt() stops
closing the socket; the QRG latches now count one value each.

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

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

github_docs/en-Changelog.md

@@ -48,6 +48,8 @@ Several operators sharing one computer can now use their own callsigns, locators
 - **No second-category locator any more:** internally there was a setting for a separate locator of the second chat category that appeared neither in the user interface nor in `preferences.xml`, so it always kept its compiled-in default. During login that default was compared with the station's locator and a warning was emitted that the second locator is ignored. ON4KST uses one locator per TCP session anyway; the setting and the warning are removed. This fixes [Issue #104](https://github.com/praktimarc/kst4contest/issues/104).
 - **Linux beta packages upgrade to the stable package:** DEB and RPM packages of a beta tag carried the same version number as the following stable package, so `dnf` and `dpkg` refused the upgrade as an equal version. Beta packages now carry a pre-release number (`1.50.0-0.beta.001`) below the stable package (`1.50.0-1`), and the release run aborts when the tag does not match `composePackageVersion`. This fixes [Issue #113](https://github.com/praktimarc/kst4contest/issues/113).
 
+- **UCXLog packets are no longer cut off:** after a short UDP packet, the listener for UCXLog-compatible loggers read every longer following packet only up to the length of the short one, so log entries could arrive incomplete. In addition, disconnecting now closes the listener's socket immediately instead of waiting for the next timeout. UCXLog packets and AirScout replies are now always decoded as UTF-8 instead of the system default, so umlauts in station names and operator callsigns no longer turn into garbage on Windows. This fixes [Issue #115](https://github.com/praktimarc/kst4contest/issues/115).
+
 ### Upgrade notes
 
 - Existing installations are **not** modified: `preferences.xml` and `praktiKST.db` stay exactly where they are and become the **Default** profile. No file is moved or copied.