Merge META-INF/services in shaded uber-JAR

Add ServicesResourceTransformer so overlapping service-provider files
(e.g. java.security.Provider) are concatenated rather than clobbered,
future-proofing the single executable JAR build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ts3-client/swing/pom.xml

@@ -66,6 +66,10 @@
                                         <Enable-Native-Access>ALL-UNNAMED</Enable-Native-Access>
                                     </manifestEntries>
                                 </transformer>
+                                <!-- Merge overlapping META-INF/services entries (e.g. java.security.Provider)
+                                     instead of letting one dependency's file overwrite another's. -->
+                                <transformer
+                                        implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                             </transformers>
                         </configuration>
                     </execution>