Add test-app module with initial UI and backend setup

Introduced a new `test-app` module with a basic Kotlin/JS UI and a Kotlin/JVM backend. Updated dependencies to use `api` where applicable and made configuration changes to support composite builds.

.idea/gradle.xml

@@ -4,11 +4,22 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
-        <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleHome" value="" />
+        <compositeConfiguration>
+          <compositeBuild compositeDefinitionSource="SCRIPT">
+            <builds>
+              <build path="$PROJECT_DIR$" name="vst-ui-base">
+                <projects>
+                  <project path="$PROJECT_DIR$" />
+                </projects>
+              </build>
+            </builds>
+          </compositeBuild>
+        </compositeConfiguration>
+        <option name="externalProjectPath" value="$PROJECT_DIR$/test-app" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
+            <option value="$PROJECT_DIR$/test-app" />
           </set>
         </option>
       </GradleProjectSettings>

.idea/kotlinc.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="KotlinJpsPluginSettings">
-    <option name="version" value="1.9.23" />
+    <option name="version" value="2.1.0" />
   </component>
 </project>