Widen the header and collapse blacklist listings by default

- the header row is no longer capped at 1600px, so the nav hugs the left
  edge and the status/account controls the right; main content and footer
  keep their width
- OnlinePage's blacklist chips and the Followed page's blacklisted-tag
  cloud start collapsed behind a count toggle (N tags / N entries)

frontend/src/components/AppShell.tsx

@@ -113,7 +113,7 @@ export function AppShell() {
   return (
     <div className="flex min-h-screen flex-col">
       <header className="sticky top-0 z-40 border-b border-ctp-surface0 bg-ctp-crust/95 backdrop-blur">
-        <div className="mx-auto flex h-14 w-full max-w-[1600px] items-center gap-4 px-4">
+        <div className="flex h-14 w-full items-center gap-4 px-3 sm:px-4">
           <Link to="/" className="flex shrink-0 items-center">
             <span className="rounded bg-ctp-mauve px-2 py-1 font-mono text-xs font-bold tracking-wide text-ctp-crust">
               J621