Initial PayGuard fraud detection system implementation

- Complete dual-layer architecture for fraud detection
- Phase 1: Docker Compose infrastructure (Kafka, Zookeeper, Redis)
- Phase 2: Mock ML models (Layer 1 fast, Layer 2 deep)
- Phase 3: FastAPI transaction ingestion with JWT auth
- Phase 4: Kafka consumer pipeline with feature extraction
- Phase 5: Test transaction producer with demo scenarios
- Phase 6: Clean code structure and comprehensive documentation
- Phase 7: End-to-end validation and demo readiness

Demonstrates key system design patterns:
- Microservices architecture with decoupled components
- Asynchronous event processing via Kafka
- Tiered decision-making (fast path vs deep analysis)
- Resilience patterns (circuit breaker for graceful degradation)
- Behavioral profiling with Redis caching

Ready for academic demonstration with clear pipeline observability.

Co-authored-by: Copilot <[email protected]>

docker-compose.yml

@@ -0,0 +1,55 @@
+version: "3.8"
+
+services:
+  zookeeper:
+    image: confluentinc/cp-zookeeper:7.5.0
+    environment:
+      ZOOKEEPER_CLIENT_PORT: 2181
+      ZOOKEEPER_TICK_TIME: 2000
+    ports:
+      - "2181:2181"
+    networks:
+      - payguard-network
+
+  kafka:
+    image: confluentinc/cp-kafka:7.5.0
+    depends_on:
+      - zookeeper
+    ports:
+      - "9092:9092"
+    environment:
+      KAFKA_BROKER_ID: 1
+      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
+      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:29092,PLAINTEXT_HOST://localhost:9092
+      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
+      KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
+      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
+      KAFKA_AUTO_CREATE_TOPICS_ENABLE: "true"
+    networks:
+      - payguard-network
+    healthcheck:
+      test: kafka-broker-api-versions --bootstrap-server localhost:9092
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
+  redis:
+    image: redis:7.2-alpine
+    ports:
+      - "6379:6379"
+    networks:
+      - payguard-network
+    healthcheck:
+      test: redis-cli ping
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    volumes:
+      - redis_data:/data
+
+volumes:
+  redis_data:
+
+networks:
+  payguard-network:
+    driver: bridge