Add thread view with replies

- Click note content to open thread view
- ThreadView shows root note, reply composer, and replies
- fetchReplies added to nostr lib (kind 1 #e filter)
- UI store gains openThread, goBack, previousView for navigation history
- Profile back button now returns to previous view correctly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/feed/NoteCard.tsx

@@ -19,7 +19,7 @@ export function NoteCard({ event }: NoteCardProps) {
   const time = event.created_at ? timeAgo(event.created_at) : "";
 
   const { loggedIn } = useUserStore();
-  const { openProfile } = useUIStore();
+  const { openProfile, openThread, currentView } = useUIStore();
   const likedKey = "wrystr_liked";
   const getLiked = () => {
     try { return new Set<string>(JSON.parse(localStorage.getItem(likedKey) || "[]")); }
@@ -109,7 +109,12 @@ export function NoteCard({ event }: NoteCardProps) {
             <span className="text-text-dim text-[11px] shrink-0">{time}</span>
           </div>
 
-          <NoteContent content={event.content} />
+          <div
+            className="cursor-pointer"
+            onClick={() => openThread(event, currentView as "feed" | "profile")}
+          >
+            <NoteContent content={event.content} />
+          </div>
 
           {/* Actions */}
           {loggedIn && (