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.

infrastructure/monitoring/monitoring-client/build.gradle.kts

@@ -1,26 +1,22 @@
+// Dieses Modul ist eine wiederverwendbare Bibliothek, die von jedem Microservice
+// eingebunden wird, um Metriken und Tracing-Daten zu exportieren.
 plugins {
-//    kotlin("jvm")
-//    kotlin("plugin.spring")
-
     alias(libs.plugins.kotlin.jvm)
     alias(libs.plugins.kotlin.spring)
-
-    // KORREKTUR: Dieses Plugin ist entscheidend. Es schaltet den `springBoot`-Block
-    // und alle Spring-Boot-spezifischen Gradle-Tasks frei.
     alias(libs.plugins.spring.boot)
-
-    // Dependency Management für konsistente Spring-Versionen
     alias(libs.plugins.spring.dependencyManagement)
 }
 
 dependencies {
+    // Stellt sicher, dass alle Versionen aus der zentralen BOM kommen.
+    implementation(platform(projects.platform.platformBom))
+    // Stellt gemeinsame Abhängigkeiten bereit.
     implementation(projects.platform.platformDependencies)
 
-    implementation("org.springframework.boot:spring-boot-starter-actuator")
-    implementation("io.micrometer:micrometer-registry-prometheus")
-    implementation("io.zipkin.reporter2:zipkin-reporter-brave")
-    implementation("io.zipkin.reporter2:zipkin-sender-okhttp3")
-    implementation("io.micrometer:micrometer-tracing-bridge-brave")
+    // OPTIMIERUNG: Verwendung des `monitoring-client`-Bundles.
+    // Es enthält Spring Boot Actuator, Micrometer Prometheus und Zipkin Tracing.
+    implementation(libs.bundles.monitoring.client)
 
+    // Stellt alle Test-Abhängigkeiten gebündelt bereit.
     testImplementation(projects.platform.platformTesting)
 }