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-bom/build.gradle.kts

@@ -1,22 +1,28 @@
+// Dieses Modul definiert die "Bill of Materials" (BOM) für das gesamte Projekt.
+// Es nutzt das `java-platform`-Plugin, um eine zentrale Liste von Abhängigkeitsversionen
+// zu erstellen, die von allen anderen Modulen importiert wird.
+// Dies ist die ultimative "Single Source of Truth" für Versionen.
 plugins {
     `java-platform`
-    `maven-publish`
+    `maven-publish` // Nützlich, falls die BOM extern veröffentlicht werden soll
 }
 
 javaPlatform {
+    // Erlaubt die Deklaration von Abhängigkeiten in einer Plattform.
     allowDependencies()
 }
 
 dependencies {
-    // KORREKTUR: Alle BOMs werden jetzt über Aliase aus der libs.versions.toml bezogen.
+    // Importiert andere wichtige BOMs. Die Versionen werden durch diese
+    // importierten Plattformen transitiv verwaltet.
     api(platform(libs.spring.boot.dependencies))
+    api(platform(libs.spring.cloud.dependencies)) // NEU: Spring Cloud BOM hinzugefügt
     api(platform(libs.kotlin.bom))
     api(platform(libs.kotlinx.coroutines.bom))
 
+    // `constraints` erzwingt spezifische Versionen für einzelne Bibliotheken.
+    // Alle Versionen werden sicher aus `libs.versions.toml` bezogen.
     constraints {
-        // KORREKTUR: Alle Abhängigkeiten verwenden jetzt Aliase.
-        // Keine einzige hartcodierte Version mehr in dieser Datei!
-
         // --- Utilities & Other ---
         api(libs.caffeine)
         api(libs.reactor.kafka)
@@ -26,16 +32,16 @@ dependencies {
         api(libs.consul.client)
         api(libs.kotlin.logging.jvm)
         api(libs.jakarta.annotation.api)
+        api(libs.auth0.java.jwt)
+        api(libs.logback.classic)
 
         // --- Spring & SpringDoc ---
         api(libs.springdoc.openapi.starter.common)
         api(libs.springdoc.openapi.starter.webmvc.ui)
 
         // --- Database & Persistence ---
-        api(libs.exposed.core)
-        api(libs.exposed.dao)
-        api(libs.exposed.jdbc)
-        api(libs.exposed.kotlin.datetime)
+        api(libs.bundles.exposed)
+        api(libs.bundles.flyway)
         api(libs.postgresql.driver)
         api(libs.hikari.cp)
         api(libs.h2.driver)
@@ -50,12 +56,11 @@ dependencies {
         api(libs.jackson.datatype.jsr310)
 
         // --- Testcontainers ---
-        api(libs.testcontainers.core)
-        api(libs.testcontainers.junit.jupiter)
-        api(libs.testcontainers.postgresql)
+        api(libs.bundles.testcontainers)
     }
 }
 
+// Konfiguration für das Veröffentlichen der BOM (optional, aber gute Praxis).
 publishing {
     publications {
         create<MavenPublication>("maven") {