fix: pskreporter — eliminate @spots crash, duplicate stream IDs, and slow aggregate blocking with start_async

lib/microwaveprop_web/live/pskr_spots_live.ex

@@ -16,18 +16,35 @@ defmodule MicrowavepropWeb.PskrSpotsLive do
     _ = if connected?(socket), do: schedule_refresh()
 
     spots = fetch_recent_spots()
+    socket = start_async(socket, :total_spots, fn -> fetch_total_spots() end)
+    socket = start_async(socket, :band_counts, fn -> fetch_band_counts() end)
 
     {:ok,
      socket
      |> assign(
        page_title: "PSK Reporter Spots",
        limit: @limit,
-       total_spots: fetch_total_spots(),
-       band_counts: fetch_band_counts()
+       total_spots: nil,
+       band_counts: [],
+       spots_empty: spots == []
      )
      |> stream(:spots, spots, reset: true)}
   end
 
+  @impl true
+  def handle_async(:total_spots, {:ok, total}, socket) do
+    {:noreply, assign(socket, total_spots: total)}
+  end
+
+  def handle_async(:band_counts, {:ok, counts}, socket) do
+    {:noreply, assign(socket, band_counts: counts)}
+  end
+
+  def handle_async(slot, {:exit, reason}, socket) do
+    Logger.warning("PskrSpotsLive async #{slot} failed: #{inspect(reason)}")
+    {:noreply, socket}
+  end
+
   @impl true
   def handle_info(:refresh_spots, socket) do
     _ = schedule_refresh()
@@ -37,7 +54,8 @@ defmodule MicrowavepropWeb.PskrSpotsLive do
      socket
      |> assign(
        total_spots: fetch_total_spots(),
-       band_counts: fetch_band_counts()
+       band_counts: fetch_band_counts(),
+       spots_empty: spots == []
      )
      |> stream(:spots, spots, reset: true)}
   end
@@ -112,13 +130,6 @@ defmodule MicrowavepropWeb.PskrSpotsLive do
             </tr>
           </thead>
           <tbody id="pskr-spots" phx-update="stream">
-            <tr
-              :for={{dom_id, spot} <- @streams.spots}
-              id={dom_id}
-              class="hidden only:table-row"
-            >
-              No spots yet
-            </tr>
             <tr :for={{dom_id, spot} <- @streams.spots} id={dom_id}>
               <td class="text-xs font-mono">{fmt_dt(spot.last_spot_at)}</td>
               <td class="text-xs"><span class="badge badge-sm">{spot.band}</span></td>
@@ -141,7 +152,7 @@ defmodule MicrowavepropWeb.PskrSpotsLive do
         </table>
       </div>
 
-      <p :if={@spots == []} class="text-sm text-base-content/50 italic mt-4">
+      <p :if={@spots_empty && @total_spots == 0} class="text-sm text-base-content/50 italic mt-4">
         No PSK Reporter spots received yet. The MQTT listener is running — spots will appear here as they arrive.
       </p>
     </Layouts.app>