Fix web UI messaging, alias resolution, and onboarding

Messaging:
- Append \n to WS IPC sends so bufio.Scanner fires (messages from web
  were silently dropped — the line scanner never saw a newline)
- Handle session_ready in web store to update peer aliases after hello

Alias resolution:
- Seed AddPeer alias from SQLite cache so returning peers resolve
  immediately, before hello exchange completes
- Remove stale SavePeer call from AddPeer (was writing placeholder IDs)
- Add PeerAlias() point-lookup to store

Onboarding redesign:
- Three-state UI: disconnected (daemon instructions), connecting,
  connected-no-network (join form)
- Read ?n= / ?network= / ?anchor= / ?invite=waste:... URL params to
  pre-fill the join form for invite links
- Show daemon alias + peer ID before any network is joined
  (master_alias + master_id now included in state_snapshot)
- Identity backup: export (passphrase-protected yaw-key-backup-1 JSON,
  download button) and restore (paste + passphrase verify)

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

internal/store/store.go

@@ -77,6 +77,13 @@ func (s *Store) SavePeer(peerID proto.PeerID, alias string) error {
 	return err
 }
 
+// PeerAlias returns the cached alias for a peer, or "" if unknown.
+func (s *Store) PeerAlias(peerID proto.PeerID) string {
+	var alias string
+	s.db.QueryRow(`SELECT alias FROM peers WHERE peer_id = ?`, string(peerID)).Scan(&alias) //nolint:errcheck
+	return alias
+}
+
 // RecentMessages returns up to limit messages for a room, oldest first.
 func (s *Store) RecentMessages(room string, limit int) ([]proto.ChatMessage, error) {
 	rows, err := s.db.Query(