fix: handle device deletion during discovery

Previously, if a device was deleted while a discovery job was in progress, the wait_loop would crash with Ecto.NoResultsError when trying to check if discovery had completed.

Now uses get_device_with_details which returns nil for missing devices, and gracefully returns {:error, :device_deleted} instead of crashing.

lib/towerops/workers/discovery_worker.ex

@@ -395,21 +395,30 @@ defmodule Towerops.Workers.DiscoveryWorker do
 
       # Check if discovery completed (last_discovery_at changed)
       true ->
-        device = Devices.get_device!(device_id)
+        case Devices.get_device_with_details(device_id) do
+          nil ->
+            Logger.warning(
+              "Device not found for discovery request",
+              device_id: device_id
+            )
 
-        if device.last_discovery_at == initial_discovery_at do
-          # Wait 500ms before checking again
-          Process.sleep(500)
-          wait_loop(device_id, agent_token_id, initial_discovery_at, start_time, timeout_ms)
-        else
-          Logger.info(
-            "Agent discovery completed successfully",
-            device_id: device_id,
-            agent_token_id: agent_token_id,
-            elapsed_ms: elapsed
-          )
+            {:error, :device_deleted}
 
-          :ok
+          device ->
+            if device.last_discovery_at == initial_discovery_at do
+              # Wait 500ms before checking again
+              Process.sleep(500)
+              wait_loop(device_id, agent_token_id, initial_discovery_at, start_time, timeout_ms)
+            else
+              Logger.info(
+                "Agent discovery completed successfully",
+                device_id: device_id,
+                agent_token_id: agent_token_id,
+                elapsed_ms: elapsed
+              )
+
+              :ok
+            end
         end
     end
   end