Keep feed note actions persistently visible

Open thread, Copy link, and Bookmark were shown only on hover via
opacity-0/group-hover, making them undiscoverable on desktop without
a mouse and unreachable for touch-only users. They're now always
visible.

Fixes #52

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BYiUtZMQeA5RHggQw73wto

src/components/nostr/NoteCard.tsx

@@ -51,7 +51,7 @@ export function NoteCard({ event, compact, className }: NoteCardProps) {
         <NoteContent content={event.content} />
 
         {!compact && (
-          <div className="mt-2 flex items-center gap-1 opacity-0 transition-opacity focus-within:opacity-100 group-hover:opacity-100">
+          <div className="mt-2 flex items-center gap-1">
             <Button
               variant="ghost"
               size="sm"