BIZ8-11 增强采购项目关联

server/prisma/migrations/20260513214500_biz8_purchase_project_link/migration.sql

@@ -0,0 +1,9 @@
+-- BIZ8-11: align purchase requests with the existing lightweight project-link pattern.
+ALTER TABLE "purchase_requests" ADD COLUMN "project_id" UUID;
+
+CREATE INDEX "idx_purchase_requests_project" ON "purchase_requests"("project_id");
+
+ALTER TABLE "purchase_requests"
+  ADD CONSTRAINT "purchase_requests_project_id_fkey"
+  FOREIGN KEY ("project_id") REFERENCES "projects"("id")
+  ON DELETE SET NULL ON UPDATE CASCADE;