more postgresql type fixes

db/helpers_sql_builder_test.go

@@ -22,3 +22,13 @@ GROUP BY`) {
 		t.Fatalf("unexpected final GROUP BY after agg/totals join; this breaks Postgres SQLSTATE 42803")
 	}
 }
+
+func TestBuildMonthlySummaryInsertCastsSampleSumToBigInt(t *testing.T) {
+	query, err := BuildMonthlySummaryInsert("inventory_monthly_summary_202601", "SELECT 1")
+	if err != nil {
+		t.Fatalf("BuildMonthlySummaryInsert failed: %v", err)
+	}
+	if !strings.Contains(query, `CAST(SUM("SamplesPresent") AS BIGINT) AS "SamplesPresent"`) {
+		t.Fatalf("expected monthly sample sum cast to BIGINT to avoid Postgres numeric assignment issues")
+	}
+}