Open WebUI

I want to install and try Open WebUI on my own computer.

Official repository: https://github.com/open-webui/open-webui
Official site: https://openwebui.com
License: Open WebUI License (custom)

Before you do anything:
1. Read the README and install notes in the official repository above, and nothing else. Do not follow third-party tutorials or mirrors.
2. Tell me in plain words what will be installed, what it needs (operating system, memory, graphics card, disk space, accounts) and what it will cost me, if anything.
3. Check my computer against those needs and tell me honestly if it will not work well.

Run it with Docker. First check whether Docker is installed and running, and if it is not, guide me through installing Docker Desktop. Use the official Docker or compose instructions from the README, keep the data in a volume so it survives updates, and tell me the address to open in my browser. Tell me how much memory and disk it will use, and how to remove it cleanly.

Rules:
- Show me each command before you run it, and say what it does.
- Ask before anything that deletes files, changes system settings, opens a network port or needs an administrator password.
- Never put my passwords or keys on a command line, or in a file I did not choose.
- When it is installed, help me check it with one small test, and tell me how to start and stop it.
- If something goes wrong, explain it in plain words and do not guess your way around it.

Good to know before you start: The license is custom, not a standard open-source one, so read it before you use it commercially. It is the interface only: you still need a model behind it.