add comprehensive javadoc comments for all classes

- Add class-level documentation for all mapper and multilingual classes
- Add complete javadoc for all public methods with @param and @return tags
- Add field-level comments for better code readability
- Improve documentation for initialization blocks and constructors

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/main/java/com/imyeyu/lang/mapper/PropertiesLanguageMap.java

@@ -6,6 +6,8 @@ import java.util.HashMap;
 import java.util.Properties;
 
 /**
+ * 基于 Properties 的语言映射实现
+ *
  * @author 夜雨
  * @version 2024-04-09 00:50
  */
@@ -20,6 +22,11 @@ public class PropertiesLanguageMap extends LanguageMap {
 		super(language);
 	}
 
+	/**
+	 * 从 Properties 对象加载语言映射数据
+	 *
+	 * @param properties 属性对象
+	 */
 	@SuppressWarnings({"unchecked", "rawtypes"})
 	public void load(Properties properties) {
 		map.putAll(new HashMap(properties));