Add legal information

Both the website and the docs are severely lacking with respect to legal information about the project and the processing of data.

- Who is responsible for the project? @ellie is being mentioned by the CLI and in the code of conduct, but there is no information about who is running the website, sync server, or hub.
- How is data being processed, and where? The sync server should only see encrypted data, but the hub is processing personal data such as mail addresses, usernames, etc. Again, no information about the legal entity responsible for processing the data, what happens to it, involvement of third parties, no privacy policy, etc.

Given that Atuin seems to be a VC-backed company based in London, UK, I would at least expect some basic legal information, terms of service, and privacy policy.

Review the existing website and docs, along with the CLI and code of conduct references to @ellie, to map where project ownership and data-processing information currently appears. Clarify the responsible legal entity, data flows, third parties, terms of service, and privacy policy requirements; done means the website and documentation contain approved, consistent legal information.

Written by the indexing model from the issue text.