fix: merge LanguageTool language-module.properties in shadow JAR

DuplicatesStrategy.INCLUDE caused multiple language-module.properties
entries in the shadow JAR. Java classloader picked only the last one
(Russian), so TypoDiagnostic failed with 'en-US is not a language code
known to LanguageTool'.

Add PropertiesFileTransformer with Append merge strategy to properly
combine all LanguageTool language classes into a single properties file.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: nixel2007

build.gradle.kts

@@ -143,11 +143,16 @@ tasks.jar {
 
 tasks.shadowJar {
     duplicatesStrategy = DuplicatesStrategy.INCLUDE
-    mergeServiceFiles() // Критично для плагинов Sonar
+    mergeServiceFiles()
     transform(com.github.jengelman.gradle.plugins.shadow.transformers.AppendingTransformer::class.java) {
         resource.set("META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports")
         separator.set("\n")
     }
+    transform(com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer::class.java) {
+        paths.set(setOf("META-INF/org/languagetool/language-module.properties"))
+        mergeStrategy.set(com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer.MergeStrategy.Append)
+        mergeSeparator.set(",")
+    }
     configurations = listOf(project.configurations["runtimeClasspath"])
     archiveClassifier.set("")
 }