coollabsio/shoutrrr ? reverse-engineered prompt

Build me a self hostable social media scheduling app where I can connect my accounts, write a post once, and publish it to multiple platforms from one calendar.

I want it to support posting to X, Bluesky, LinkedIn, Facebook, Instagram, Threads, and Discord, with the ability to schedule posts for later, set recurring time slots, and publish immediately if needed. It should let me create workspaces for different brands or clients, invite teammates, and keep everything separated by workspace. I also want a simple composer with media upload, alt text, and a live preview of how the post will look on each account, including any length limits. If a post fails or an account needs reconnecting, show clear notifications.

Please make it easy to run on my own server, ideally with Docker, and keep the data private on my side. If you need to check current docs or API details while building, feel free to look them up online.