feat(build): Refactor infrastructure modules and establish single source of truth

This commit introduces a major refactoring of the build system and the core infrastructure modules. The primary goal is to establish a strict "Single Source of Truth" for all dependencies using Gradle Version Catalogs and to create a clean, maintainable, and scalable foundation for all current and future services.

### 1. Centralized Dependency Management (`libs.versions.toml`)

- **Established Single Source of Truth:** All dependency versions are now exclusively managed in `gradle/libs.versions.toml`. Hardcoded versions have been removed from all build scripts.
- **Introduced Gradle Bundles:** To simplify module dependencies, several bundles have been created (e.g., `testing-jvm`, `redis-cache`, `spring-cloud-gateway`, `monitoring-client`). This drastically reduces boilerplate in the `build.gradle.kts` files and improves readability.
- **Cleaned up Aliases:** All library and plugin aliases have been standardized for consistency.

### 2. Infrastructure Module Refactoring

All infrastructure modules (`core`, `platform`, `auth`, `cache`, `event-store`, `messaging`, `monitoring`, `gateway`) have been refactored to align with the new dependency management strategy.

- **Simplified Build Scripts:** The `build.gradle.kts` for each module now uses the new bundles and aliases, making them significantly cleaner and easier to understand.
- **Consistent Structure:** The architecture of each module now clearly follows the Port-Adapter pattern where applicable (e.g., `cache-api`/`redis-cache`).
- **Standardized `platform-bom`:** The project's own Bill of Materials (`platform-bom`) now also includes the Spring Cloud BOM, ensuring version consistency for all Spring-related dependencies.

### 3. Added Infrastructure Documentation

To improve onboarding and architectural understanding, a dedicated `README-*.md` file has been created for each refactored infrastructure module:
- `README-CORE.md`
- `README-PLATFORM.md`
- `README-INFRA-AUTH.md`
- `README-INFRA-CACHE.md`
- `README-INFRA-EVENT-STORE.md`
- `README-INFRA-MESSAGING.md`
- `README-INFRA-MONITORING.md`
- `README-INFRA-GATEWAY.md`

These documents explain the purpose, architecture, and usage of each component within the system. This lays the groundwork for our "Tracer Bullet" development approach.

platform/platform-testing/build.gradle.kts

@@ -1,26 +1,21 @@
-plugins {
-    // KORREKTUR: 'java-library' und 'kotlin("jvm")' ersetzen
+/*plugins {
     alias(libs.plugins.kotlin.multiplatform)
 }
 
 kotlin {
-    // KORREKTUR: JVM- und JS-Ziele definieren
     jvm()
     js(IR) {
         browser()
     }
 
     sourceSets {
-        // Diese Abhängigkeiten sind für alle Plattformen (JVM, JS) verfügbar
         val commonTest by getting {
             dependencies {
-                // Die 'kotlin("test")'-Abhängigkeit ist der Standardweg für KMP-Tests
                 implementation(kotlin("test"))
                 api(libs.kotlinx.coroutines.test)
             }
         }
 
-        // Diese Abhängigkeiten sind NUR für die JVM-Tests verfügbar
         val jvmTest by getting {
             dependencies {
                 api(libs.junit.jupiter.api)
@@ -28,7 +23,6 @@ kotlin {
                 api(libs.junit.jupiter.params)
                 api(libs.junit.platform.launcher)
 
-                // KORREKTUR: Alle hartcodierten Versionen durch Aliase ersetzen
                 api(libs.mockk)
                 api(libs.assertj.core)
                 api(libs.spring.boot.starter.test)
@@ -40,4 +34,24 @@ kotlin {
             }
         }
     }
+}*/
+
+// Dieses Modul bündelt alle für JVM-Tests notwendigen Abhängigkeiten.
+// Jedes Modul, das Tests enthält, sollte dieses Modul mit `testImplementation` einbinden.
+plugins {
+    alias(libs.plugins.kotlin.jvm)
+}
+
+dependencies {
+    // Importiert die zentrale BOM für konsistente Versionen.
+    api(platform(projects.platform.platformBom))
+
+    // OPTIMIERUNG: Verwendung von Bundles, um die Konfiguration zu vereinfachen.
+    // Diese Bundles sind in `libs.versions.toml` definiert.
+    api(libs.bundles.testing.jvm)
+    api(libs.bundles.testcontainers)
+
+    // Einzelne Test-Abhängigkeiten, die nicht in den Haupt-Bundles enthalten sind.
+    api(libs.spring.boot.starter.test)
+    api(libs.h2.driver) // H2 wird oft für In-Memory-Tests benötigt.
 }