refactor: Is.get_status pattern-matches on process presence

The original get_status/0 had a nested case/try that duplicated the
"disconnected" status map across two branches. Split into:

- status_from/1 with nil + is_pid heads for the "no GenServer" and
  "GenServer alive" paths. The alive path isolates the catch :exit, _
  fallback for a non-responding process.
- disconnected_status/1 builds the shared status map once, parameterised
  on the default server string to preserve the original branch-specific
  fallback behavior.

Removes ~20 duplicated lines; all 61 Is tests still pass.

lib/aprsme/is/is.ex

@@ -125,50 +125,40 @@ defmodule Aprsme.Is do
   end
 
   def get_status do
-    case Process.whereis(__MODULE__) do
+    status_from(Process.whereis(__MODULE__))
-      nil ->
+  end
-        # GenServer is not running (disconnected)
-        server = Application.get_env(:aprsme, :aprs_is_server, nil)
-        port = Application.get_env(:aprsme, :aprs_is_port, 14_580)
-        {stored_packet_count, oldest_packet_timestamp} = safe_packet_storage_stats()
 
-        %{
+  # GenServer isn't running — return a disconnected snapshot.
-          connected: false,
+  defp status_from(nil), do: disconnected_status(nil)
-          server: server_to_string(server),
-          port: port,
-          connected_at: nil,
-          uptime_seconds: 0,
-          login_id: Application.get_env(:aprsme, :aprs_is_login_id, "W5ISP"),
-          filter: Application.get_env(:aprsme, :aprs_is_default_filter, "r/33/-96/100"),
-          packet_stats: default_packet_stats(),
-          stored_packet_count: stored_packet_count,
-          oldest_packet_timestamp: oldest_packet_timestamp
-        }
 
-      _pid ->
+  defp status_from(pid) when is_pid(pid) do
-        try do
+    GenServer.call(__MODULE__, :get_status, 5000)
-          GenServer.call(__MODULE__, :get_status, 5000)
+  catch
-        catch
+    # GenServer exists but isn't responding — treat as disconnected but
-          :exit, _ ->
+    # fall back to the rotate.aprs2.net default server string.
-            # GenServer exists but not responding
+    :exit, _ -> disconnected_status(~c"rotate.aprs2.net")
-            server = Application.get_env(:aprsme, :aprs_is_server, ~c"rotate.aprs2.net")
+  end
-            port = Application.get_env(:aprsme, :aprs_is_port, 14_580)
-            {stored_packet_count, oldest_packet_timestamp} = safe_packet_storage_stats()
 
-            %{
+  # Build the "I'm not connected" status map. `default_server` is only used
-              connected: false,
+  # when the application config has no server set; pass nil to mean "use
-              server: server_to_string(server),
+  # whatever is in config, or nil".
-              port: port,
+  defp disconnected_status(default_server) do
-              connected_at: nil,
+    server = Application.get_env(:aprsme, :aprs_is_server, default_server)
-              uptime_seconds: 0,
+    port = Application.get_env(:aprsme, :aprs_is_port, 14_580)
-              login_id: Application.get_env(:aprsme, :aprs_is_login_id, "W5ISP"),
+    {stored_packet_count, oldest_packet_timestamp} = safe_packet_storage_stats()
-              filter: Application.get_env(:aprsme, :aprs_is_default_filter, "r/33/-96/100"),
+
-              packet_stats: default_packet_stats(),
+    %{
-              stored_packet_count: stored_packet_count,
+      connected: false,
-              oldest_packet_timestamp: oldest_packet_timestamp
+      server: server_to_string(server),
-            }
+      port: port,
-        end
+      connected_at: nil,
-    end
+      uptime_seconds: 0,
+      login_id: Application.get_env(:aprsme, :aprs_is_login_id, "W5ISP"),
+      filter: Application.get_env(:aprsme, :aprs_is_default_filter, "r/33/-96/100"),
+      packet_stats: default_packet_stats(),
+      stored_packet_count: stored_packet_count,
+      oldest_packet_timestamp: oldest_packet_timestamp
+    }
   end
 
   defp safe_packet_storage_stats do