fix: use runtime env config in YamlProfiles init (broken in releases)

Mix isn't loaded in mix releases, so Mix.env() raised
UndefinedFunctionError inside YamlProfiles.init/1, crashing the
GenServer at boot. That made Supervisor.start_link return {:error, ...}
in production, which the application-start callback then masked by
exiting on the unrelated Task.Supervisor.start_child noproc — leaving
the pod in CrashLoopBackoff with no clear log of the real failure.

Switch to Application.get_env(:towerops, :env), which is set in all
three environments (dev/test/runtime).

Also harden the post-startup callback so a transient TaskSupervisor
noproc cannot mask a real Supervisor.start_link error in the future.

lib/towerops/application.ex

@@ -142,21 +142,33 @@ defmodule Towerops.Application do
     opts = [strategy: :one_for_one, name: Towerops.Supervisor]
     result = Supervisor.start_link(children, opts)
 
-    # Attach telemetry filter to suppress noisy health check logs
-    ToweropsWeb.TelemetryFilter.attach()
-
-    # Run post-startup cleanup tasks (production only)
-    # This ensures all polling jobs use the latest worker code after deployment
-    _ =
-      Task.Supervisor.start_child(Towerops.TaskSupervisor, fn ->
-        # Wait for supervisor to fully initialize
-        Process.sleep(2000)
-        JobCleanupTask.run()
-      end)
+    if match?({:ok, _}, result), do: post_startup()
 
     result
   end
 
+  # Post-startup work runs only when the supervisor came up cleanly. The Task
+  # supervisor call is wrapped in try/catch so a transient noproc (the named
+  # supervisor may not be ready or may already be dying) cannot exit the boot
+  # process and mask the real error from Supervisor.start_link.
+  defp post_startup do
+    ToweropsWeb.TelemetryFilter.attach()
+
+    _ =
+      try do
+        Task.Supervisor.start_child(Towerops.TaskSupervisor, fn ->
+          Process.sleep(2000)
+          JobCleanupTask.run()
+        end)
+      catch
+        :exit, reason ->
+          Logger.warning("Skipping JobCleanupTask: #{inspect(reason)}")
+          :error
+      end
+
+    :ok
+  end
+
   # Tell Phoenix to update the endpoint configuration
   # whenever the application is updated.
   @impl true

lib/towerops/profiles/yaml_profiles.ex

@@ -89,7 +89,8 @@ defmodule Towerops.Profiles.YamlProfiles do
   def init(_opts) do
     _ = :ets.new(@table, [:named_table, :set, :public, read_concurrency: true])
 
-    if Mix.env() == :test do
+    # Mix isn't loaded in releases — use the runtime app env instead.
+    if Application.get_env(:towerops, :env) == :test do
       # Load synchronously so tests don't race with deferred loading.
       raw_profiles = load_all_profiles()
       mib_names = extract_mib_names_from_profiles(raw_profiles)