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/dto/AgentInstanceResponse.java

@@ -13,7 +13,7 @@ import java.util.Map;
 public record AgentInstanceResponse(
         @NotNull String id,
         @NotNull String name,
-        @NotNull String group,
+        @NotNull String application,
         @NotNull String status,
         @NotNull List<String> routeIds,
         @NotNull Instant registeredAt,
@@ -29,7 +29,7 @@ public record AgentInstanceResponse(
     public static AgentInstanceResponse from(AgentInfo info) {
         long uptime = Duration.between(info.registeredAt(), Instant.now()).toSeconds();
         return new AgentInstanceResponse(
-                info.id(), info.name(), info.group(),
+                info.id(), info.name(), info.application(),
                 info.state().name(), info.routeIds(),
                 info.registeredAt(), info.lastHeartbeat(),
                 info.version(), info.capabilities(),
@@ -41,7 +41,7 @@ public record AgentInstanceResponse(
 
     public AgentInstanceResponse withMetrics(double tps, double errorRate, int activeRoutes) {
         return new AgentInstanceResponse(
-                id, name, group, status, routeIds, registeredAt, lastHeartbeat,
+                id, name, application, status, routeIds, registeredAt, lastHeartbeat,
                 version, capabilities,
                 tps, errorRate, activeRoutes, totalRoutes, uptimeSeconds
         );

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

@@ -10,7 +10,7 @@ import java.util.Map;
 public record AgentRegistrationRequest(
         @NotNull String agentId,
         @NotNull String name,
-        @Schema(defaultValue = "default") String group,
+        @Schema(defaultValue = "default") String application,
         String version,
         List<String> routeIds,
         Map<String, Object> capabilities