fix: make agent schedule migration idempotent for production

Use DO blocks with EXCEPTION WHEN duplicate_column to safely handle
columns that may already exist from a previous db push.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/prisma/migrations/20260426130000_add_agent_schedule_fields/migration.sql

@@ -1,4 +1,15 @@
--- AlterTable: Agent
-ALTER TABLE "Agent" ADD COLUMN "scheduledTime" TEXT DEFAULT '08:00';
-ALTER TABLE "Agent" ADD COLUMN "scheduledDay" INTEGER;
-ALTER TABLE "Agent" ADD COLUMN "timezone" TEXT;
+-- AlterTable: Agent (idempotent — safe if columns already exist from a previous db push)
+DO $$ BEGIN
+  ALTER TABLE "Agent" ADD COLUMN "scheduledTime" TEXT DEFAULT '08:00';
+EXCEPTION WHEN duplicate_column THEN NULL;
+END $$;
+
+DO $$ BEGIN
+  ALTER TABLE "Agent" ADD COLUMN "scheduledDay" INTEGER;
+EXCEPTION WHEN duplicate_column THEN NULL;
+END $$;
+
+DO $$ BEGIN
+  ALTER TABLE "Agent" ADD COLUMN "timezone" TEXT;
+EXCEPTION WHEN duplicate_column THEN NULL;
+END $$;