fix(ocr): correct trainSenderModel URI from /train to /train-sender

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/service/RestClientOcrClient.java

@@ -173,7 +173,7 @@ public class RestClientOcrClient implements OcrClient, OcrHealthClient {
 
         TrainingResultJson result = addTrainingAuth(
                 trainingRestClient.post()
-                        .uri("/train")
+                        .uri("/train-sender")
                         .contentType(MediaType.MULTIPART_FORM_DATA))
                 .body(body)
                 .retrieve()

backend/src/test/java/org/raddatz/familienarchiv/service/RestClientOcrClientTrainingTest.java

@@ -0,0 +1,41 @@
+package org.raddatz.familienarchiv.service;
+
+import com.sun.net.httpserver.HttpServer;
+import org.junit.jupiter.api.Test;
+
+import java.io.OutputStream;
+import java.net.InetSocketAddress;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RestClientOcrClientTrainingTest {
+
+    @Test
+    void trainSenderModel_postsToTrainSenderEndpoint() throws Exception {
+        List<String> capturedPaths = new CopyOnWriteArrayList<>();
+        HttpServer server = HttpServer.create(new InetSocketAddress(0), 0);
+        server.createContext("/", exchange -> {
+            capturedPaths.add(exchange.getRequestURI().getPath());
+            byte[] response = "{\"loss\":0.1,\"accuracy\":0.95,\"cer\":0.05,\"epochs\":3}"
+                    .getBytes(StandardCharsets.UTF_8);
+            exchange.getResponseHeaders().set("Content-Type", "application/json");
+            exchange.sendResponseHeaders(200, response.length);
+            try (OutputStream os = exchange.getResponseBody()) {
+                os.write(response);
+            }
+        });
+        server.start();
+
+        try {
+            int port = server.getAddress().getPort();
+            RestClientOcrClient client = new RestClientOcrClient("http://localhost:" + port, "");
+            client.trainSenderModel(new byte[]{1, 2, 3}, "/app/models/sender_test.mlmodel");
+            assertThat(capturedPaths).contains("/train-sender");
+        } finally {
+            server.stop(0);
+        }
+    }
+}