feat(r3): complete order and payment flow

prisma/migrations/20260913113000_payment_timeout/migration.sql

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+-- 待付款订单统一在服务端以创建后 30 分钟为截止时间，避免只由客户端倒计时控制。
+ALTER TYPE "OrderStatus" ADD VALUE IF NOT EXISTS 'PAYMENT_EXPIRED';
+
+ALTER TABLE "Order" ADD COLUMN IF NOT EXISTS "paymentExpiresAt" TIMESTAMP(3);
+
+-- 为已有待付款订单补齐截止时间；历史订单会按创建时间计算并在下一次读取时自动过期。
+UPDATE "Order"
+SET "paymentExpiresAt" = "createdAt" + INTERVAL '30 minutes'
+WHERE "paymentExpiresAt" IS NULL AND "status" = 'PENDING';
+
+CREATE INDEX IF NOT EXISTS "Order_paymentExpiresAt_idx" ON "Order"("paymentExpiresAt");