Zero-config backends on Vercel AI Cloud

Introduces zero-configuration deployment for Python (FastAPI, Flask) and TypeScript (Express, Hono, NestJS, Nitro) backends on Vercel AI Cloud. Leverages Framework-Defined Infrastructure (FDI) to automatically provision and scale infrastructure based on framework conventions. Extends Fluid Compute with Active CPU Pricing for intermittent workloads, billing only for active execution time. Introduces the Workflow Development Kit (WDK) for durable orchestration of long-running backends and background agents. Offers new backend AI templates for patterns like RAG pipelines.