refactor: Migrate from monolithic to modular architecture

1. **Docker-Compose für Entwicklung optimieren**
2. **Umgebungsvariablen für lokale Entwicklung**
3. **Service-Abhängigkeiten**
4. **Docker-Compose für Produktion**
5. **Dokumentation**

config/kafka/secrets/kafka_jaas.conf

@@ -0,0 +1,20 @@
+// Kafka JAAS Configuration for Production
+// =============================================================================
+// This file configures SASL authentication for Kafka in production
+// Change the passwords to strong, randomly generated values
+// =============================================================================
+
+KafkaServer {
+    org.apache.kafka.common.security.plain.PlainLoginModule required
+    username="admin"
+    password="CHANGE_ME_STRONG_KAFKA_ADMIN_PASSWORD"
+    user_admin="CHANGE_ME_STRONG_KAFKA_ADMIN_PASSWORD"
+    user_producer="CHANGE_ME_STRONG_KAFKA_PRODUCER_PASSWORD"
+    user_consumer="CHANGE_ME_STRONG_KAFKA_CONSUMER_PASSWORD";
+};
+
+Client {
+    org.apache.kafka.common.security.plain.PlainLoginModule required
+    username="admin"
+    password="CHANGE_ME_STRONG_KAFKA_ADMIN_PASSWORD";
+};

config/kafka/secrets/zookeeper_jaas.conf

@@ -0,0 +1,17 @@
+// Zookeeper JAAS Configuration for Production
+// =============================================================================
+// This file configures SASL authentication for Zookeeper in production
+// Change the passwords to strong, randomly generated values
+// =============================================================================
+
+Server {
+    org.apache.zookeeper.server.auth.DigestLoginModule required
+    user_admin="CHANGE_ME_STRONG_ZOOKEEPER_ADMIN_PASSWORD"
+    user_kafka="CHANGE_ME_STRONG_ZOOKEEPER_KAFKA_PASSWORD";
+};
+
+Client {
+    org.apache.zookeeper.server.auth.DigestLoginModule required
+    username="kafka"
+    password="CHANGE_ME_STRONG_ZOOKEEPER_KAFKA_PASSWORD";
+};