Build a Subscription-Based SaaS Platform for Hosted Apps with Large File Processing

Hi, I want to build a subscription-based SaaS platform where I can host and manage my own apps/tools, while users access them based on their subscription plan. The platform should have two sides. On the admin side, I should be able to connect/register apps from my GitHub or other repositories, manage apps, manage users, assign plans, control access, view jobs/files/logs, and manage usage limits. On the user side, customers should only log in, see the apps allowed by their plan, upload files, run jobs, track progress, and download results. Users should not interact with GitHub, backend, deployment, or technical settings. The platform should include user authentication, admin dashboard, user dashboard, Stripe or similar subscription payments, app categories, plan-based permissions, admin-only GitHub app registration, large-file upload, cloud object storage, background job processing, job status tracking, usage limits, result downloads, and live deployment under my domain/subdomain. The strongest requirement is large-file support. Some files may be around 1.5 GB or larger, so uploads should use Cloudflare R2, AWS S3, or Google Cloud Storage with signed URLs, multipart/resumable upload if possible, and progress tracking. I do not want a simple upload form that crashes on large files. Preferred stack is FastAPI or Django, React/Next.js, PostgreSQL, Redis/Celery, Docker, Cloudflare R2 or AWS S3, and Stripe, but I am open to your recommendation. Please share your fixed price, timeline, proposed architecture, and experience with SaaS platforms, large-file uploads, subscriptions, GitHub integration, background jobs, and cloud deployment.