feature: Outbox Relay and Kafka Pipeline

docker-compose.yml

@@ -19,11 +19,38 @@ services:
     image: datalust/seq:latest
     environment:
       ACCEPT_EULA: "Y"
+      SEQ_FIRSTRUN_ADMINPASSWORD: "admin"
     ports:
       - "5345:80"
     volumes:
       - seq_data:/data
 
+  kafka:
+    image: apache/kafka:3.7.0
+    ports:
+      - "9092:9092"
+    environment:
+      KAFKA_NODE_ID: 1
+      KAFKA_PROCESS_ROLES: broker,controller
+      KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092,CONTROLLER://0.0.0.0:9093
+      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:9092
+      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,CONTROLLER:PLAINTEXT
+      KAFKA_CONTROLLER_QUORUM_VOTERS: 1@kafka:9093
+      KAFKA_CONTROLLER_LISTENER_NAMES: CONTROLLER
+      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
+      KAFKA_TRANSACTION_STATE_LOG_REPLICATION_FACTOR: 1
+      KAFKA_TRANSACTION_STATE_LOG_MIN_ISR: 1
+      # Disable auto-creation — topics are provisioned explicitly with the correct
+      # partition count. Auto-creation would silently create a topic with 1 partition
+      # if the relay publishes before the provisioner runs.
+      KAFKA_AUTO_CREATE_TOPICS_ENABLE: "false"
+      # Fixed ID prevents the broker from reinitializing storage on restart.
+      # Generate once with: kafka-storage.sh random-uuid | base64
+      CLUSTER_ID: "MkU3OEVBNTcwNTJENDM2Qk"
+    volumes:
+      - kafka_data:/var/lib/kafka/data
+
 volumes:
   pg_data:
-  seq_data:
+  seq_data:
+  kafka_data: