Add kafka-streams module: fraud detection topology tested with TopologyTestDriver

Similarity scoring, a 5-minute windowed count that alerts once, and a KTable
blocklist join, with the Spring wiring on Spring Boot 4.1.1 and Kafka Streams 4.2.1.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01RjfyTgmERTWLqzafu34Cth

kafka-streams/src/test/java/com/ankurm/streams/ContextLoadsTest.java

@@ -0,0 +1,27 @@
+package com.ankurm.streams;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.kafka.config.StreamsBuilderFactoryBean;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/** Proves the Spring wiring: the factory bean exists and holds a topology, without a broker. */
+@SpringBootTest
+class ContextLoadsTest {
+
+    @Autowired ApplicationContext ctx;
+
+    @Test
+    void streamsFactoryBeanIsWiredAndNotStarted() throws Exception {
+        var t = new Transcript("06-spring-context.txt");
+        var fb = ctx.getBean(StreamsBuilderFactoryBean.class);
+        t.line("StreamsBuilderFactoryBean present: " + (fb != null));
+        t.line("auto-startup: " + fb.isAutoStartup());
+        t.line("running: " + fb.isRunning());
+        t.write();
+        assertFalse(fb.isRunning());
+    }
+}