refactor(training): extract kurrentLabels helper + clarify query comments

Extract repeated `new java.util.HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION))`
into a `kurrentLabels()` helper in TrainingBlockQueryTest and add `import java.util.HashSet`.

Add clarifying comments on the two person-scoped queries in TranscriptionBlockRepository
explaining that they use `MEMBER OF d.trainingLabels` — aligned with the pre-existing
`findEligibleKurrentBlocks()` pattern.

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

backend/src/main/java/org/raddatz/familienarchiv/repository/TranscriptionBlockRepository.java

@@ -60,6 +60,8 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
             """)
     List<TranscriptionBlock> findSegmentationBlocks();
 
+    // Uses 'KURRENT_RECOGNITION' MEMBER OF d.trainingLabels — aligned with findEligibleKurrentBlocks()
+    // which already used this form (changed from d.scriptType = 'KURRENT' in the original queries).
     @Query("""
             SELECT COUNT(b) FROM TranscriptionBlock b
             JOIN Document d ON d.id = b.documentId
@@ -69,6 +71,8 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
             """)
     long countManualKurrentBlocksByPerson(@Param("personId") UUID personId);
 
+    // Uses 'KURRENT_RECOGNITION' MEMBER OF d.trainingLabels — aligned with findEligibleKurrentBlocks()
+    // which already used this form (changed from d.scriptType = 'KURRENT' in the original queries).
     @Query("""
             SELECT b FROM TranscriptionBlock b
             JOIN Document d ON d.id = b.documentId

backend/src/test/java/org/raddatz/familienarchiv/repository/TrainingBlockQueryTest.java

@@ -5,7 +5,6 @@ import org.junit.jupiter.api.Test;
 import org.raddatz.familienarchiv.PostgresContainerConfig;
 import org.raddatz.familienarchiv.config.FlywayConfig;
 import org.raddatz.familienarchiv.model.*;
-import java.util.Set;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.jdbc.test.autoconfigure.AutoConfigureTestDatabase;
 import org.springframework.boot.data.jpa.test.autoconfigure.DataJpaTest;
@@ -13,6 +12,7 @@ import org.springframework.context.annotation.Import;
 
 import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.UUID;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -38,7 +38,7 @@ class TrainingBlockQueryTest {
                 .title("Kurrent Brief")
                 .originalFilename("kurrent.pdf")
                 .status(DocumentStatus.UPLOADED)
-                .trainingLabels(new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION)))
+                .trainingLabels(kurrentLabels())
                 .build());
         kurrentDocId = kurrentDoc.getId();
 
@@ -123,7 +123,7 @@ class TrainingBlockQueryTest {
                 .originalFilename("karl.pdf")
                 .status(DocumentStatus.UPLOADED)
                 .sender(sender)
-                .trainingLabels(new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION)))
+                .trainingLabels(kurrentLabels())
                 .build());
         UUID annId = annotationRepository.save(annotation(doc.getId())).getId();
         blockRepository.save(block(doc.getId(), annId, BlockSource.MANUAL, false));
@@ -158,7 +158,7 @@ class TrainingBlockQueryTest {
                 .originalFilename("karl.pdf")
                 .status(DocumentStatus.UPLOADED)
                 .sender(sender)
-                .trainingLabels(new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION)))
+                .trainingLabels(kurrentLabels())
                 .build());
         UUID annId = annotationRepository.save(annotation(doc.getId())).getId();
         blockRepository.save(block(doc.getId(), annId, BlockSource.OCR, false));
@@ -177,7 +177,7 @@ class TrainingBlockQueryTest {
                 .originalFilename("karl.pdf")
                 .status(DocumentStatus.UPLOADED)
                 .sender(karl)
-                .trainingLabels(new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION)))
+                .trainingLabels(kurrentLabels())
                 .build());
         UUID annId = annotationRepository.save(annotation(doc.getId())).getId();
         blockRepository.save(block(doc.getId(), annId, BlockSource.MANUAL, false));
@@ -195,7 +195,7 @@ class TrainingBlockQueryTest {
                 .originalFilename("karl.pdf")
                 .status(DocumentStatus.UPLOADED)
                 .sender(sender)
-                .trainingLabels(new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION)))
+                .trainingLabels(kurrentLabels())
                 .build());
         UUID annId = annotationRepository.save(annotation(doc.getId())).getId();
         blockRepository.save(block(doc.getId(), annId, BlockSource.MANUAL, false));
@@ -218,6 +218,10 @@ class TrainingBlockQueryTest {
 
     // ─── helpers ─────────────────────────────────────────────────────────────
 
+    private static Set<TrainingLabel> kurrentLabels() {
+        return new HashSet<>(Set.of(TrainingLabel.KURRENT_RECOGNITION));
+    }
+
     private DocumentAnnotation annotation(UUID docId) {
         return DocumentAnnotation.builder()
                 .documentId(docId)