Update knob component defaults and clean up unused code

Adjusted the default value, minValue, and step for the volume knob to improve precision. Removed unused `KnobBackgroundCls` and cleaned up unnecessary whitespace for better readability and maintainability.

build.gradle.kts

@@ -3,7 +3,7 @@
 import org.jetbrains.kotlin.gradle.ExperimentalKotlinGradlePluginApi
 
 plugins {
-    kotlin("multiplatform") version "2.1.10"
+    kotlin("multiplatform") version "2.1.20"
     `maven-publish`
     signing
 }