Backend Development (MVP) for Creator Platform to create microsites

We are seeking a skilled Backend Developer or Agency to architect and build the RESTful API for a new SaaS platform. The product allows users to register, build customized microsites, publish categorized posts, and monetize content via Stripe. Core Features & Infrastructure Requirements: #1 Authentication & User Management: Secure registration, session handling (JWT), and user profile management. #2 Microsite Architecture: Database design and endpoints to store and retrieve user-specific microsite configurations (design settings, layouts). #3 Content Management System: Robust CRUD endpoints for managing Posts and relational Categories. #4 Stripe Integration (Payments): Deep integration with the Stripe API to handle subscriptions, paywalls, and secure webhooks for gated content. #5 Newsletter & Mailing Logic: Endpoints and background processes to handle newsletter signups and third-party mailing service integrations. #6 Analytics Tracking: Infrastructure to capture, aggregate, and serve analytics data (e.g., page views, conversion metrics) to the frontend dashboard. #7 Public Landing Page API: Necessary endpoints to serve dynamic data (e.g., pricing tiers, feature flags) to the public SaaS landing page. Technical Expectations: #1 Scalable and modern backend stack (e.g., Node.js, Python, PHP, or Go). #2 Relational database management (PostgreSQL or MySQL) with a focus on multi-tenant data security. #3 Comprehensive API documentation (Swagger/OpenAPI) and clean error handling. Application: Please provide a rough cost estimate, timeline, and your recommended tech stack based on these required features. This is backend only!