feat: persistent per-application config with GET/PUT endpoints

Add application_config table (V4 migration), repository, and REST
controller. GET /api/v1/config/{app} returns config, PUT saves and
pushes CONFIG_UPDATE to all LIVE agents via SSE. UI tracing toggle
now uses config API instead of direct SET_TRACED_PROCESSORS command.
Tracing store syncs with server config on load.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/security/SecurityConfig.java

@@ -77,6 +77,10 @@ public class SecurityConfig {
                         .requestMatchers(HttpMethod.GET, "/api/v1/search/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN", "AGENT")
                         .requestMatchers(HttpMethod.POST, "/api/v1/search/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
 
+                        // Application config endpoints
+                        .requestMatchers(HttpMethod.GET, "/api/v1/config/*").hasAnyRole("VIEWER", "OPERATOR", "ADMIN", "AGENT")
+                        .requestMatchers(HttpMethod.PUT, "/api/v1/config/*").hasAnyRole("OPERATOR", "ADMIN")
+
                         // Read-only data endpoints — viewer+
                         .requestMatchers(HttpMethod.GET, "/api/v1/executions/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")
                         .requestMatchers(HttpMethod.GET, "/api/v1/diagrams/**").hasAnyRole("VIEWER", "OPERATOR", "ADMIN")