fix: Handle both atom and string keys in weather view packet comparison

The weather view was crashing with KeyError when receiving packets with
string keys instead of atom keys. This was happening when packets were
broadcast from different parts of the system.

Changes:
- Updated should_update_weather? to handle both atom and string keys
- Added proper nil checking for received_at timestamps
- Handle string timestamp comparisons as well as DateTime comparisons

This prevents crashes when the weather view receives packets with
inconsistent key types from PubSub broadcasts.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

lib/aprsme_web/live/weather_live/callsign_view.ex

@@ -93,7 +93,23 @@ defmodule AprsmeWeb.WeatherLive.CallsignView do
 
   defp should_update_weather?(current_packet, new_packet) do
     # Only update if the new packet is actually newer
-    DateTime.after?(new_packet.received_at, current_packet.received_at)
+    # Handle both atom and string keys
+    new_received_at = Map.get(new_packet, :received_at) || Map.get(new_packet, "received_at")
+    current_received_at = Map.get(current_packet, :received_at) || Map.get(current_packet, "received_at")
+
+    case {new_received_at, current_received_at} do
+      {nil, _} ->
+        false
+
+      {_, nil} ->
+        true
+
+      {new_time, current_time} when is_binary(new_time) and is_binary(current_time) ->
+        new_time > current_time
+
+      {new_time, current_time} ->
+        DateTime.after?(new_time, current_time)
+    end
   end
 
   defp update_weather_data(socket) do