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/services/ping/ping-service/src/main/kotlin/at/mocode/ping/application/PingService.kt

@@ -3,6 +3,7 @@ package at.mocode.ping.application
 import at.mocode.ping.domain.Ping
 import at.mocode.ping.domain.PingRepository
 import org.slf4j.LoggerFactory
+import org.springframework.context.annotation.Profile
 import org.springframework.stereotype.Service
 import org.springframework.transaction.annotation.Transactional
 import kotlin.uuid.ExperimentalUuidApi
@@ -14,6 +15,7 @@ import kotlin.uuid.Uuid
  * Hier darf Spring (@Service, @Transactional) verwendet werden, da es "Application Logic" ist.
  */
 @Service
+@Profile("!test") // Nicht im Test-Profil laden, damit wir Mocks nutzen können
 @OptIn(ExperimentalUuidApi::class)
 class PingService(
     private val repository: PingRepository

backend/services/ping/ping-service/src/main/kotlin/at/mocode/ping/infrastructure/persistence/PingJpaEntity.kt

@@ -14,6 +14,10 @@ class PingJpaEntity(
     val message: String,
     val createdAt: Instant
 ) {
-    // Default constructor for JPA
-    protected constructor() : this(UUID.randomUUID(), "", Instant.now())
+    // The default constructor for JPA
+    // Protected is fine for Hibernate, but the Kotlin compiler might complain about visibility.
+    // We can make it private or internal if needed, but protected is standard.
+    // To suppress the warning "effectively private", we can just leave it as is or make it public/internal.
+    // Let's try making it internal to satisfy Kotlin while keeping it hidden from public API.
+    internal constructor() : this(UUID.randomUUID(), "", Instant.now())
 }

backend/services/ping/ping-service/src/main/kotlin/at/mocode/ping/infrastructure/persistence/PingRepositoryAdapter.kt

@@ -2,6 +2,7 @@ package at.mocode.ping.infrastructure.persistence
 
 import at.mocode.ping.domain.Ping
 import at.mocode.ping.domain.PingRepository
+import org.springframework.context.annotation.Profile
 import org.springframework.stereotype.Repository
 import kotlin.uuid.ExperimentalUuidApi
 import kotlin.uuid.Uuid
@@ -10,6 +11,7 @@ import kotlin.uuid.toKotlinUuid
 
 @OptIn(ExperimentalUuidApi::class)
 @Repository
+@Profile("!test") // Nicht im Test-Profil laden, damit wir Mocks nutzen können
 class PingRepositoryAdapter(
     private val jpaRepository: SpringDataPingRepository
 ) : PingRepository {

backend/services/ping/ping-service/src/main/kotlin/at/mocode/ping/infrastructure/web/PingController.kt

@@ -83,6 +83,7 @@ class PingController(
     )
 
     // Fallback
+    @Suppress("unused", "UNUSED_PARAMETER")
     fun fallbackPing(simulate: Boolean, ex: Exception): EnhancedPingResponse {
         logger.warn("Circuit breaker fallback triggered: {}", ex.message)
         return EnhancedPingResponse(