fix(training): use KURRENT_RECOGNITION label for sender-based block queries

scriptType is only set after OCR runs, which can't happen before we have
a trained model. Both sender-based queries now filter on the training label
instead, consistent with findEligibleKurrentBlocks.

Also adds missing test coverage for findManualKurrentBlocksByPerson and
countManualKurrentBlocksByPerson (4 cases + count parity check).

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

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

@@ -65,7 +65,7 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
             JOIN Document d ON d.id = b.documentId
             WHERE b.source = 'MANUAL'
             AND d.sender.id = :personId
-            AND d.scriptType = 'HANDWRITING_KURRENT'
+            AND 'KURRENT_RECOGNITION' MEMBER OF d.trainingLabels
             """)
     long countManualKurrentBlocksByPerson(@Param("personId") UUID personId);
 
@@ -74,7 +74,7 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
             JOIN Document d ON d.id = b.documentId
             WHERE b.source = 'MANUAL'
             AND d.sender.id = :personId
-            AND d.scriptType = 'HANDWRITING_KURRENT'
+            AND 'KURRENT_RECOGNITION' MEMBER OF d.trainingLabels
             """)
     List<TranscriptionBlock> findManualKurrentBlocksByPerson(@Param("personId") UUID personId);
 }