chore: opportunity for monorepo-wide dead code cleanup with knip

`npx knip` reports a large amount of potentially removable dead code across the monorepo (~357 unused files, ~83 unused dependencies, ~64 unused devDependencies on current `master` [my local is a dozen commits behind but it around this area]). From my experience using knip on other repositories, unused dependencies tend to have false positives but unused files are usually pretty accurate. To validate, I picked a random file that it flagged: [apps/www/components/BackedBy.tsx](https://github.com/supabase/supabase/blob/master/apps/www/components/BackedBy.tsx) (~3 years old). Global search for `BackedBy` returns no imports/usages outside the file itself. The commit [f26761121a](https://github.com/supabase/supabase/commit/f26761121ad57b9ddda0c7c478920770a7817b79) is the commit that removed the last invocation of the BackedBy component. Knip was added in #35072 and there has been recent studio-focused cleanup (#47122, #47387, #47399), but there doesn't appear to be a tracking issue for monorepo-wide dead code removal especially outside `apps/studio`. I think there's significant cleanup opportunity in `apps/www`, `apps/docs`, `apps/design-system`, etc.), much of it likely leftover from App Router / component migrations.