feat(#119): accept route states in heartbeat and state-change events

Replace ACK-based route state inference with agent-reported state.
Heartbeats now carry optional routeStates map, and ROUTE_STATE_CHANGED
events update the registry immediately.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/dto/HeartbeatRequest.java

@@ -0,0 +1,7 @@
+package com.cameleer3.server.app.dto;
+
+import java.util.Map;
+
+public record HeartbeatRequest(
+    Map<String, String> routeStates
+) {}