Restore account requirement for NIP-29 groups

NIP-29 groups are membership-based and relay-enforced, so they should
require an active account to view. This restores the account check
in resolveConversation() for NIP-29 while keeping other protocols
(like NIP-53 live chat) viewable without authentication.

src/lib/chat/adapters/nip-29-adapter.ts

@@ -116,6 +116,11 @@ export class Nip29Adapter extends ChatProtocolAdapter {
       throw new Error("NIP-29 groups require a relay URL");
     }
 
+    const activePubkey = accountManager.active$.value?.pubkey;
+    if (!activePubkey) {
+      throw new Error("No active account");
+    }
+
     console.log(
       `[NIP-29] Fetching group metadata for ${groupId} from ${relayUrl}`,
     );