feat(design): titles in click surfaces stay selectable (E28 S3e4b)

A button whose text is a title or a name is now `selectable` (FocusSafeButton,
under Pressable and Button): Chrome selects inside a button once it is
user-select: text (measured), and the click that ends a selection, or a press
dragged past the slop, opens nothing. 23 surfaces carry it (cards, rows, people,
channels, playlists, users, views, messages, log lines, description links); the
Plex caption div gets the same guard. A contract test pins every plain Pressable
with its reason, so a new one has to choose.

frontend/src/components/Stats.tsx

@@ -336,6 +336,7 @@ function UserRow({ row, max }: { row: AdminQuotaRow; max: number }) {
   return (
     <div className={`${SURFACE.card} p-3`}>
       <Pressable
+        selectable
         onClick={() => setOpen((o) => !o)}
         aria-expanded={open}
         className="w-full flex items-center gap-3"