chore: add migration 0007 for amount_aud + exchange_rate_to_aud columns

prisma/migrations/0007_cashflow/migration.sql

@@ -0,0 +1,7 @@
+-- Add FX conversion support
+ALTER TABLE statements ADD COLUMN IF NOT EXISTS exchange_rate_to_aud NUMERIC(10,6);
+ALTER TABLE transactions ADD COLUMN IF NOT EXISTS amount_aud NUMERIC(12,2);
+
+-- Backfill: all existing data is AUD
+UPDATE transactions SET amount_aud = amount WHERE amount_aud IS NULL;
+UPDATE statements SET exchange_rate_to_aud = 1.000000 WHERE exchange_rate_to_aud IS NULL;