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/test/java/com/cameleer3/server/app/TestSecurityHelper.java

@@ -37,8 +37,8 @@ public class TestSecurityHelper {
     /**
      * Returns a valid JWT access token with the given roles (no agent registration).
      */
-    public String createToken(String subject, String group, List<String> roles) {
-        return jwtService.createAccessToken(subject, group, roles);
+    public String createToken(String subject, String application, List<String> roles) {
+        return jwtService.createAccessToken(subject, application, roles);
     }
 
     /**