refactor: AbstractInflowControlManager 상속 구조 리팩토링 및 커맨드 클래스 타입 변경

InflowControlManager에서 공통 로직을 AbstractInflowControlManager로 분리하고,
커맨드 클래스들이 AbstractInflowControlManager 타입을 사용하도록 변경.
InflowControlUtil에 cachedInflowControlManager 정적 캐시 도입.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main/java/com/eactive/eai/agent/inflow/RemoveInflowClientControlCommand.java

@@ -2,7 +2,8 @@ package com.eactive.eai.agent.inflow;
 
 import com.eactive.eai.agent.command.Command;
 import com.eactive.eai.agent.command.CommandException;
-import com.eactive.eai.common.inflow.InflowControlManager;
+import com.eactive.eai.common.inflow.AbstractInflowControlManager;
+import com.eactive.eai.common.inflow.InflowControlUtil;
 import com.eactive.eai.common.inflow.dual.DualInflowControlManager;
 import com.eactive.eai.common.util.Logger;
 
@@ -29,7 +30,7 @@ public class RemoveInflowClientControlCommand extends Command {
 
 		String key = (String) args;
 		try {
-			InflowControlManager base = InflowControlManager.getInstance();
+			AbstractInflowControlManager base = InflowControlUtil.getInflowControlManager();
 			if (!(base instanceof DualInflowControlManager)) {
 				throw new IllegalStateException("DualInflowControlManager 가 활성화되지 않았습니다.");
 			}