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>

ui/src/api/schema.d.ts

@@ -625,10 +625,10 @@ export interface paths {
             cookie?: never;
         };
         /**
-         * Find diagram by application group and route ID
-         * @description Resolves group to agent IDs and finds the latest diagram for the route
+         * Find diagram by application and route ID
+         * @description Resolves application to agent IDs and finds the latest diagram for the route
          */
-        get: operations["findByGroupAndRoute"];
+        get: operations["findByApplicationAndRoute"];
         put?: never;
         post?: never;
         delete?: never;
@@ -683,7 +683,7 @@ export interface paths {
         };
         /**
          * List all agents
-         * @description Returns all registered agents with runtime metrics, optionally filtered by status and/or group
+         * @description Returns all registered agents with runtime metrics, optionally filtered by status and/or application
          */
         get: operations["listAgents"];
         put?: never;
@@ -1158,7 +1158,7 @@ export interface components {
             agentId: string;
             name: string;
             /** @default default */
-            group: string;
+            application: string;
             version?: string;
             routeIds?: string[];
             capabilities?: {
@@ -1384,7 +1384,7 @@ export interface components {
         AgentInstanceResponse: {
             id: string;
             name: string;
-            group: string;
+            application: string;
             status: string;
             routeIds: string[];
             /** Format: date-time */
@@ -3133,10 +3133,10 @@ export interface operations {
             };
         };
     };
-    findByGroupAndRoute: {
+    findByApplicationAndRoute: {
         parameters: {
             query: {
-                group: string;
+                application: string;
                 routeId: string;
             };
             header?: never;
@@ -3154,7 +3154,7 @@ export interface operations {
                     "*/*": components["schemas"]["DiagramLayout"];
                 };
             };
-            /** @description No diagram found for the given group and route */
+            /** @description No diagram found for the given application and route */
             404: {
                 headers: {
                     [name: string]: unknown;
@@ -3239,7 +3239,7 @@ export interface operations {
         parameters: {
             query?: {
                 status?: string;
-                group?: string;
+                application?: string;
             };
             header?: never;
             path?: never;