Reduce cyclomatic complexity in high-complexity functions

Extract helper functions to reduce complexity in functions with
complexity 10-15:

- packet.ex: Extract add_symbol_data/2
  Moves symbol data extraction into separate function
  Reduces complexity from 10 to 9

- mobile_channel.ex: Extract bounds validation helpers
  Creates all_numeric?/4, valid_latitudes?/2, valid_longitudes?/2
  Moves complex boolean conditions into readable helper functions
  Reduces complexity from 15 to within limits

- historical_loader.ex: Extract packet_has_valid_coordinates?/1
  Moves coordinate validation logic with multiple conditions
  Reduces complexity from 15 to within limits

Fixes 3 more Credo cyclomatic complexity issues.

lib/aprsme/packet.ex

@@ -323,10 +323,7 @@ defmodule Aprsme.Packet do
 
     # Check if symbol data exists at the top level of attrs (from APRS parser)
     # and preserve it if not already in base_attrs
-    base_attrs =
-      base_attrs
-      |> maybe_put(:symbol_code, attrs[:symbol_code] || attrs["symbol_code"])
-      |> maybe_put(:symbol_table_id, attrs[:symbol_table_id] || attrs["symbol_table_id"])
+    base_attrs = add_symbol_data(base_attrs, attrs)
 
     # Extract data based on the type of data_extended
     additional_data =
@@ -352,6 +349,12 @@ defmodule Aprsme.Packet do
     merge_extracted_data(base_attrs, additional_data, attrs)
   end
 
+  defp add_symbol_data(base_attrs, attrs) do
+    base_attrs
+    |> maybe_put(:symbol_code, attrs[:symbol_code] || attrs["symbol_code"])
+    |> maybe_put(:symbol_table_id, attrs[:symbol_table_id] || attrs["symbol_table_id"])
+  end
+
   defp merge_extracted_data(base_attrs, additional_data, attrs) do
     # Process telemetry fields from top-level attrs if not already processed
     telemetry_data =

lib/aprsme_web/channels/mobile_channel.ex

@@ -243,13 +243,13 @@ defmodule AprsmeWeb.MobileChannel do
 
   defp validate_bounds(%{north: north, south: south, east: east, west: west}) do
     cond do
-      not is_number(north) or not is_number(south) or not is_number(east) or not is_number(west) ->
+      not all_numeric?(north, south, east, west) ->
         {:error, "All bounds must be numeric"}
 
-      north < -90 or north > 90 or south < -90 or south > 90 ->
+      not valid_latitudes?(north, south) ->
         {:error, "Latitude must be between -90 and 90"}
 
-      east < -180 or east > 180 or west < -180 or west > 180 ->
+      not valid_longitudes?(east, west) ->
         {:error, "Longitude must be between -180 and 180"}
 
       north <= south ->
@@ -260,6 +260,18 @@ defmodule AprsmeWeb.MobileChannel do
     end
   end
 
+  defp all_numeric?(north, south, east, west) do
+    is_number(north) and is_number(south) and is_number(east) and is_number(west)
+  end
+
+  defp valid_latitudes?(north, south) do
+    north >= -90 and north <= 90 and south >= -90 and south <= 90
+  end
+
+  defp valid_longitudes?(east, west) do
+    east >= -180 and east <= 180 and west >= -180 and west <= 180
+  end
+
   defp ensure_float(value) when is_integer(value), do: value * 1.0
   defp ensure_float(value) when is_float(value), do: value
   defp ensure_float(value) when is_binary(value), do: String.to_float(value)

lib/aprsme_web/live/map_live/historical_loader.ex

@@ -172,14 +172,7 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
         packet_data_list =
           try do
             # Filter out packets with invalid coordinates before processing
-            valid_packets =
-              Enum.filter(historical_packets, fn packet ->
-                {lat, lon, _} = CoordinateUtils.get_coordinates(packet)
-
-                is_number(lat) and is_number(lon) and
-                  lat >= -90 and lat <= 90 and lon >= -180 and lon <= 180 and
-                  is_finite(lat) and is_finite(lon)
-              end)
+            valid_packets = Enum.filter(historical_packets, &packet_has_valid_coordinates?/1)
 
             if length(valid_packets) < length(historical_packets) do
               Logger.debug(
@@ -450,4 +443,12 @@ defmodule AprsmeWeb.MapLive.HistoricalLoader do
 
   defp is_finite(n) when is_float(n), do: n != :infinity and n != :neg_infinity
   defp is_finite(n) when is_integer(n), do: true
+
+  defp packet_has_valid_coordinates?(packet) do
+    {lat, lon, _} = CoordinateUtils.get_coordinates(packet)
+
+    is_number(lat) and is_number(lon) and
+      lat >= -90 and lat <= 90 and lon >= -180 and lon <= 180 and
+      is_finite(lat) and is_finite(lon)
+  end
 end