fix: QA issues — composite index, anchors, fallbacks

- Add composite index ix_translation_records_run_source_hash
  for NOT EXISTS dedup subquery performance + Alembic migration
- Remove duplicate #endregion in orchestrator.py (INV_3)
- Replace hardcoded RU fallback 'Статус' with 'Status'
- Add early return guard to loadMoreRecords()
- Show records summary always when recordsTotal > 0

backend/alembic/versions/c7d8e9f0a1b2_add_run_source_hash_composite_index.py

@@ -0,0 +1,38 @@
+"""Add composite index (run_id, source_hash) for NOT EXISTS dedup
+
+Adds ix_translation_records_run_source_hash on translation_records(run_id, source_hash)
+to accelerate the correlated NOT EXISTS subquery in orchestrator_query.get_run_records
+when deduplicate=true.
+
+Revision ID: c7d8e9f0a1b2
+Revises: a1b2c3d4e5f6
+Create Date: 2026-06-04 13:30:00.000000
+
+"""
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "c7d8e9f0a1b2"
+down_revision: str | Sequence[str] | None = "a1b2c3d4e5f6"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Create composite index."""
+    op.create_index(
+        "ix_translation_records_run_source_hash",
+        "translation_records",
+        ["run_id", "source_hash"],
+        postgresql_using="btree",
+        sqlite=True,
+    )
+
+
+def downgrade() -> None:
+    """Drop composite index."""
+    op.drop_index("ix_translation_records_run_source_hash",
+                  table_name="translation_records")