A self-hosted search page that dispatches queries to whichever site you meant, using DuckDuckGo-style bang shortcuts you define yourself.
Bang shortcuts are the fastest way to search a specific site, but they mean routing every query through someone else's engine and accepting the shortcuts they chose to support.
Shortcuts are a JSON file you own, each a URL template the query is substituted into, so adding one is an edit rather than a feature request.
A query with no shortcut falls through to a default engine, so it can be set as the browser's search provider and never gets in the way.
One Go binary with the page and stylesheet embedded, so there is nothing to serve alongside it.