feat(catalog): preserve and display dataset value scores

backend/migrations/versions/0009_dataset_value_score.py

@@ -0,0 +1,17 @@
+"""Preserve the upstream dataset value score; old snapshots remain unknown."""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0009"
+down_revision = "0008"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column("catalog_entries", sa.Column("value_score", sa.Float(), nullable=True))
+
+
+def downgrade():
+    op.drop_column("catalog_entries", "value_score")