refactor: rename agent group→application across entire codebase

Complete the group→application terminology rename in the agent
registry subsystem:

- AgentInfo: field group → application, all wither methods updated
- AgentRegistryService: findByGroup → findByApplication
- AgentInstanceResponse: field group → application (API response)
- AgentRegistrationRequest: field group → application (API request)
- JwtServiceImpl: parameter names group → application (JWT claim
  string "group" preserved for token backward compatibility)
- All controllers, lifecycle monitor, command controller updated
- Integration tests: JSON request bodies "group" → "application"
- Frontend: schema.d.ts, openapi.json, agent queries, AgentHealth

RBAC group references (groups table, GroupAdminController, etc.)
are NOT affected — they are a separate domain concept.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/agent/AgentLifecycleMonitor.java

@@ -51,7 +51,7 @@ public class AgentLifecycleMonitor {
                 if (before != null && before != agent.state()) {
                     String eventType = mapTransitionEvent(before, agent.state());
                     if (eventType != null) {
-                        agentEventService.recordEvent(agent.id(), agent.group(), eventType,
+                        agentEventService.recordEvent(agent.id(), agent.application(), eventType,
                                 agent.name() + " " + before + " -> " + agent.state());
                     }
                 }