Add follow/unfollow (NIP-02) from profile view

- publishContactList (kind 3) in nostr lib — replaces full follow list on each change
- follow() and unfollow() actions in user store with optimistic UI update
- Follow/Unfollow button in ProfileView header (visible when logged in, not own profile)
- Button shows "unfollow" in muted style with danger hover when already following

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

src/lib/nostr/client.ts

@@ -191,6 +191,17 @@ export async function fetchUserNotes(pubkey: string, limit = 30): Promise<NDKEve
   return Array.from(events).sort((a, b) => (b.created_at ?? 0) - (a.created_at ?? 0));
 }
 
+export async function publishContactList(pubkeys: string[]): Promise<void> {
+  const instance = getNDK();
+  if (!instance.signer) throw new Error("Not logged in");
+
+  const event = new NDKEvent(instance);
+  event.kind = 3;
+  event.content = "";
+  event.tags = pubkeys.map((pk) => ["p", pk]);
+  await event.publish();
+}
+
 export async function fetchProfile(pubkey: string) {
   const instance = getNDK();
   const user = instance.getUser({ pubkey });

src/lib/nostr/index.ts

@@ -1 +1 @@
-export { getNDK, connectToRelays, fetchGlobalFeed, fetchFollowFeed, fetchReplies, publishNote, publishArticle, publishProfile, publishReaction, publishReply, fetchUserNotes, fetchProfile } from "./client";
+export { getNDK, connectToRelays, fetchGlobalFeed, fetchFollowFeed, fetchReplies, publishNote, publishArticle, publishProfile, publishReaction, publishReply, publishContactList, fetchUserNotes, fetchProfile } from "./client";