Add a "my sequences page" displaying released sequences

[theosanderson]

resolves #1029

preview URL: http://mysequences.loculus.org

Summary

Creates a my sequences page that re-uses the search UI but with hidden filters to display only the group's sequences.

PR Checklist

• All necessary documentation has been adapted.
• The implemented feature is covered by an appropriate test.

[fengelniederhammer]

I didn't check the code, but the page looks good. Definitely something we can take as a base 👍

[theosanderson]

The code should be ready now. There are aspects that aren't great - some of those come from Astro limitations, but I'm sure there's some bits we can work on.

[fengelniederhammer]

Thanks 👍