Description of the bug

When self-hosting crab.fit following the self hosting instructions, the sharing link always refers to crab.fit as the TLD. This seems rooted here. I tried a quick fix, but Next.js SSR throws errors when accessing the window object. I'm not sure what style you'd like to follow to not access window on the server, so opening this issue to begin with.

To reproduce

1. Follow self-host instructions using a custom domain
2. Open App in Vercel
3. Create a crab fit
4. URL erroneously points to https://crab.fit/..

Expected behavior

The URL resolves to the current origin + path.

Additional information

No response