fix: preserve SOR execution venue separately

trex_core/adapters/persistence/sql/024_add_ledger_order_venue.sql

@@ -0,0 +1,12 @@
+-- GitHub #61: keep the original submission venue separate from actual execution venue.
+ALTER TABLE ledger_outbox
+    ADD COLUMN IF NOT EXISTS order_venue TEXT NOT NULL DEFAULT 'KRX';
+
+ALTER TABLE ledger_outbox
+    DROP CONSTRAINT IF EXISTS ledger_outbox_order_venue_check;
+ALTER TABLE ledger_outbox
+    ADD CONSTRAINT ledger_outbox_order_venue_check
+    CHECK (order_venue IN ('KRX', 'NXT', 'SOR'));
+
+-- Historical rows used venue for both concepts. Preserve that provenance.
+UPDATE ledger_outbox SET order_venue = venue WHERE order_venue = 'KRX' AND venue <> 'KRX';