Add Javadoc to ScanPropertyNames class

Add class-level documentation to clarify the purpose of ScanPropertyNames
as a container for SonarQube scan property name constants.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: romainbrenguier

src/main/java/org/sonarqube/gradle/ScanPropertyNames.java

@@ -19,6 +19,9 @@
  */
 package org.sonarqube.gradle;
 
+/**
+ * Constants for SonarQube scan property names.
+ */
 public final class ScanPropertyNames {
   // General
   public static final String SKIP = "sonar.skip";