Prioritize pending contacts over queued in backfill

Queued contacts just need reconciliation (check if data exists),
while pending contacts need actual HRRR fetches. Process pending
first so real work happens before reconciliation.

lib/microwaveprop/workers/backfill_enqueue_worker.ex

@@ -24,7 +24,7 @@ defmodule Microwaveprop.Workers.BackfillEnqueueWorker do
       Contact
       |> where([c], not is_nil(c.pos1) or not is_nil(c.grid1))
       |> where(^type_filter(types))
-      |> order_by([c], desc: c.qso_timestamp)
+      |> order_by(^status_priority_order(types))
       |> limit(^limit)
       |> Repo.all()
 
@@ -48,6 +48,16 @@ defmodule Microwaveprop.Workers.BackfillEnqueueWorker do
 
   defp parse_types(_), do: [:hrrr, :weather, :terrain, :iemre]
 
+  defp status_priority_order(types) do
+    # Prioritize pending/failed over queued so real work happens first
+    field = :"#{hd(types)}_status"
+
+    [
+      asc: dynamic([c], fragment("CASE ? WHEN 'pending' THEN 0 WHEN 'failed' THEN 1 ELSE 2 END", field(c, ^field))),
+      desc: dynamic([c], c.qso_timestamp)
+    ]
+  end
+
   defp type_filter(types) do
     Enum.reduce(types, dynamic(false), fn type, acc ->
       field = :"#{type}_status"