Make migration 0161 re-runnable with IF NOT EXISTS

The reorder_lead_days column add used a bare ADD COLUMN; match 0160's
idempotent guard so a re-run is safe. Schema unchanged, SQL-only.

prisma/migrations/0161_v1170_reorder_lead_days/migration.sql

@@ -16,4 +16,4 @@
 -- up without a migration of its own.
 
 ALTER TABLE "medications"
-  ADD COLUMN "reorder_lead_days" INTEGER;
+  ADD COLUMN IF NOT EXISTS "reorder_lead_days" INTEGER;