fix: make spatial packet tests robust against :process_batch mailbox pollution

Replace assert_receive with a receive_spatial_packet helper that ignores
:process_batch messages. These are scheduled by handle_events via
Process.send_after and can pollute the test process mailbox when tests
run in the full test suite.

test/aprsme/packet_consumer_test.exs

@@ -533,7 +533,7 @@ defmodule Aprsme.PacketConsumerTest do
       Process.sleep(50)
 
       # Should receive the packet via PubSub with object_name as sender
-      assert_receive {:spatial_packet, packet}, 1000
+      packet = receive_spatial_packet()
       assert packet.sender == "CALGRY", "Expected sender to be object name CALGRY, got #{packet.sender}"
       assert packet.latitude == 51.044733
       assert packet.longitude == -114.062019
@@ -573,7 +573,7 @@ defmodule Aprsme.PacketConsumerTest do
       Process.sleep(50)
 
       # Should receive the packet via PubSub with item_name as sender
-      assert_receive {:spatial_packet, packet}, 1000
+      packet = receive_spatial_packet()
       assert packet.sender == "MyItem", "Expected sender to be item name MyItem, got #{packet.sender}"
       assert packet.latitude == 35.0
       assert packet.longitude == -75.0
@@ -807,7 +807,7 @@ defmodule Aprsme.PacketConsumerTest do
       Process.sleep(50)
 
       # Should receive the packet via PubSub
-      assert_receive {:spatial_packet, packet}, 1000
+      packet = receive_spatial_packet()
       assert packet.sender == "BROADCAST1"
     end
 
@@ -940,7 +940,7 @@ defmodule Aprsme.PacketConsumerTest do
       # Wait for async broadcast task to complete
       Process.sleep(50)
 
-      assert_receive {:spatial_packet, packet}, 1000
+      packet = receive_spatial_packet()
       assert packet.sender == "FALLBACK1"
     end
   end
@@ -1003,4 +1003,15 @@ defmodule Aprsme.PacketConsumerTest do
     on_exit(fn -> SpatialPubSub.unregister_client(client_id) end)
     :ok
   end
+
+  # Receives a spatial packet, ignoring :process_batch messages
+  # that may be in the mailbox from handle_events scheduling.
+  defp receive_spatial_packet(timeout \\ 2000) do
+    receive do
+      {:spatial_packet, packet} -> packet
+      :process_batch -> receive_spatial_packet(timeout)
+    after
+      timeout -> flunk("Expected {:spatial_packet, _} but did not receive one within #{timeout}ms")
+    end
+  end
 end