perf: optimize map LiveView hot paths

Remove unused 30s timer, skip heatmap recluster on every single packet, trail dedup O(n^2)->O(n)

Ultraworked with Sisyphus

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

lib/aprsme_web/live/map_live/display_manager.ex

@@ -161,7 +161,10 @@ defmodule AprsmeWeb.MapLive.DisplayManager do
 
   defp trail_packets_for_callsign(visible_packets, historical_packets, callsign, threshold) do
     (Map.values(visible_packets) ++ Map.values(historical_packets))
-    |> Enum.uniq_by(&trail_packet_key/1)
+    |> Enum.reduce(%{}, fn p, acc ->
+      Map.put_new(acc, trail_packet_key(p), p)
+    end)
+    |> Map.values()
     |> Enum.filter(&tracked_packet?(&1, callsign, threshold))
     |> Enum.sort_by(&packet_timestamp/1, :asc)
   end

lib/aprsme_web/live/map_live/index.ex

@@ -141,8 +141,6 @@ defmodule AprsmeWeb.MapLive.Index do
       _ = Aprsme.StreamingPacketsPubSub.subscribe_to_bounds(self(), default_bounds)
 
       _ = Process.send_after(self(), :cleanup_old_packets, 60_000)
-      # Schedule UI update timer to refresh "time ago" display every 30 seconds
-      _ = Process.send_after(self(), :update_time_display, 30_000)
 
       socket
       |> assign(:spatial_client_id, client_id)
@@ -830,8 +828,6 @@ defmodule AprsmeWeb.MapLive.Index do
 
   def handle_info(:cleanup_old_packets, socket), do: handle_cleanup_old_packets(socket)
 
-  def handle_info(:update_time_display, socket), do: handle_update_time_display(socket)
-
   def handle_info(:reload_historical_packets, socket), do: handle_reload_historical_packets(socket)
 
   def handle_info({:postgres_packet, packet}, socket) do
@@ -1743,13 +1739,6 @@ defmodule AprsmeWeb.MapLive.Index do
     {:noreply, assign(socket, :visible_packets, kept)}
   end
 
-  defp handle_update_time_display(socket) do
-    # Schedule next update
-    Process.send_after(self(), :update_time_display, 30_000)
-
-    {:noreply, assign(socket, :time_display_tick, System.monotonic_time())}
-  end
-
   defp handle_reload_historical_packets(socket) do
     require Logger
 
@@ -1808,15 +1797,6 @@ defmodule AprsmeWeb.MapLive.Index do
 
   # Helper functions for marker operations
 
-  @spec remove_markers_batch(Socket.t(), list()) :: Socket.t()
-  defp remove_markers_batch(socket, []), do: socket
-
-  defp remove_markers_batch(socket, marker_ids) do
-    Enum.reduce(marker_ids, socket, fn id, acc ->
-      push_event(acc, "remove_marker", %{id: id})
-    end)
-  end
-
   @spec add_markers_if_any(Socket.t(), list()) :: Socket.t()
   defp add_markers_if_any(socket, []), do: socket
 
@@ -2014,7 +1994,7 @@ defmodule AprsmeWeb.MapLive.Index do
 
     socket =
       socket
-      |> remove_markers_batch(packets_to_remove)
+      |> DisplayManager.remove_markers_batch(packets_to_remove)
       |> maybe_clear_historical_packets(bounds_state)
       |> push_event("filter_markers_by_bounds", %{bounds: map_bounds})
       |> assign(map_bounds: map_bounds, visible_packets: new_visible_packets)

lib/aprsme_web/live/map_live/packet_processor.ex

@@ -10,7 +10,6 @@ defmodule AprsmeWeb.MapLive.PacketProcessor do
   alias AprsmeWeb.Live.Shared.CoordinateUtils
   alias AprsmeWeb.Live.Shared.PacketUtils, as: SharedPacketUtils
   alias AprsmeWeb.MapLive.DataBuilder
-  alias AprsmeWeb.MapLive.DisplayManager
   alias Phoenix.LiveView
   alias Phoenix.LiveView.Socket
 
@@ -108,10 +107,7 @@ defmodule AprsmeWeb.MapLive.PacketProcessor do
     render_for_zoom(socket.assigns.map_zoom, marker_data, socket)
   end
 
-  # Zoom 8 and below use the heatmap instead of individual markers.
-  defp render_for_zoom(zoom, _marker_data, socket) when zoom <= 8 do
-    send_heat_map_for_current_bounds(socket)
-  end
+  defp render_for_zoom(zoom, _marker_data, socket) when zoom <= 8, do: socket
 
   defp render_for_zoom(_zoom, nil, socket), do: socket
 
@@ -224,10 +220,6 @@ defmodule AprsmeWeb.MapLive.PacketProcessor do
     Map.get(socket.assigns, :locale, "en")
   end
 
-  defp send_heat_map_for_current_bounds(socket) do
-    DisplayManager.send_heat_map_for_current_bounds(socket)
-  end
-
   defp send_marker_with_popup_check(socket, marker_data) do
     # Strip convert_from — the single-packet JS handler uses its own scan logic.
     marker_data = Map.delete(marker_data, "convert_from")