fix: restrict DELETE scope in removeDuplicityDescribingEntities

The DELETE query in BatchJobActivityFinalizer.removeDuplicityDescribingEntities
was missing an activity_revision_id filter on the outer WHERE clause. This
caused a full sequential scan of the entire activity_describing_entity table
(5.5 GB in production) on every batch job completion, making the query take
~9 seconds instead of <1ms.

Additionally, the missing filter meant the DELETE could affect rows from
unrelated historical activity revisions that happened to share the same
(entity_class, entity_id) as entities in the batch being merged, silently
corrupting activity history data.

Fix: add (activity_revision_id in (:revisionIds) or activity_revision_id =
:activityRevisionIdToMergeInto) as the leading predicate on the outer DELETE,
restricting it to only the chunk revisions being merged. This allows the
existing index on (activity_revision_id, entity_class, entity_id) to be used.

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

Author: dkrizan

backend/data/src/main/kotlin/io/tolgee/batch/BatchJobActivityFinalizer.kt

@@ -171,7 +171,8 @@ class BatchJobActivityFinalizer(
       .createNativeQuery(
         """
         delete from activity_describing_entity
-        where (entity_class, entity_id) in
+        where (activity_revision_id in (:revisionIds) or activity_revision_id = :activityRevisionIdToMergeInto)
+        and (entity_class, entity_id) in
               (select entity_class, entity_id
                from activity_describing_entity
                where activity_revision_id in (:revisionIds)