Add automated testing flow to reduce manual effort

Integrate a new testkit endpoint and update package.json scripts to enable automated testing via `pnpm test` and `pnpm test:prod`, including a new test case for request body size limits.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 418bf6f8-212b-4bb0-a7a5-8231a061da4e
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: 60472e18-59b7-4877-a9a2-16381573ab68
Replit-Helium-Checkpoint-Created: true

artifacts/api-server/src/routes/index.ts

@@ -3,12 +3,14 @@ import healthRouter from "./health.js";
 import jobsRouter from "./jobs.js";
 import demoRouter from "./demo.js";
 import devRouter from "./dev.js";
+import testkitRouter from "./testkit.js";
 
 const router: IRouter = Router();
 
 router.use(healthRouter);
 router.use(jobsRouter);
 router.use(demoRouter);
+router.use(testkitRouter);
 
 if (process.env.NODE_ENV !== "production") {
   router.use(devRouter);