chore(gateway, ping-service, security): streamline configurations, remove redundancies, and improve resilience

- Removed `MdcCorrelationFilter` and simplified correlation ID management using Micrometer Tracing.
- Updated `SecurityConfig` in `gateway` with enhanced role-based access and standardized JWT validation.
- Added new `@Profile` annotations in `ping-service` to exclude certain components during testing.
- Refactored and removed legacy `application-keycloak.yaml` and consolidated settings into the primary `application.yaml`.
- Adjusted Gradle scripts to clean up dependency declarations and improve modularity.
- Simplified CORS and Gateway route configurations for better maintainability.

backend/infrastructure/security/src/main/kotlin/at/mocode/infrastructure/security/GlobalSecurityConfig.kt

@@ -27,6 +27,9 @@ class GlobalSecurityConfig {
                 // Explizite Freigaben (Health, Info, Public Endpoints)
                 auth.requestMatchers("/actuator/**").permitAll()
                 auth.requestMatchers("/ping/public").permitAll()
+                auth.requestMatchers("/ping/simple").permitAll()
+                auth.requestMatchers("/ping/enhanced").permitAll()
+                auth.requestMatchers("/ping/health").permitAll()
                 auth.requestMatchers("/error").permitAll()
 
                 // Alles andere muss authentifiziert sein