- Server tracks callsign replacements in prepare_packet_state, sends
convert_to_historical list so JS skips full markerStates scan
- Historical packets get red dot HTML server-side in build_minimal_packet_data
instead of JS createMarkerIcon generating it
- Add callsign_group field to all packet data output; server pre-sorts
by group with chronological order so JS iterates directly
- Normalize heat map intensity in Clustering.cluster_packets (min/50, cap 1.0)
instead of JS doing it per-point
- Remove buildPopupContent JS fallback and unused escapeHtml import;
server already provides popup in all data paths
Graham McIntire
b4bbfda620