feat(server): 完成 P0+P1 后端能力（工作流、RBAC、付款归档）

P0 MVP：

- 认证：login/refresh/logout/forgot/reset + tokenVersion

- RBAC：角色到权限映射 + requirePermission

- 发票池：upload/bind/signed-url + 判重（VALID_003/VALID_005）

- 报销：create/view/submit + 单号生成

- 工作流：approve + department_manager 解析

P1 扩展：

- 动作：reject/return/withdraw（含 comment）

- transfer：任务转审 + 链路上限 3

- pay：approved -> paid + 发票归档 used_complete

- 动态审批链：approval_rules 驱动

回归脚本：

- smoke-test.sh / regression-dedup.sh / regression-workflow-actions.sh

server/src/prismaClient.js

@@ -0,0 +1,19 @@
+const { PrismaClient } = require("@prisma/client");
+const { PrismaPg } = require("@prisma/adapter-pg");
+const { Pool } = require("pg");
+
+function createPrismaClient() {
+  const connectionString = process.env.DATABASE_URL;
+  if (!connectionString) {
+    throw new Error("Missing DATABASE_URL");
+  }
+
+  const pool = new Pool({ connectionString });
+  const adapter = new PrismaPg(pool, { disposeExternalPool: false });
+  const prisma = new PrismaClient({ adapter });
+
+  return { prisma, pool };
+}
+
+module.exports = { createPrismaClient };
+