L2: Remove 2-second Process.sleep from post_startup — the try/catch
already handles transient noproc errors from the TaskSupervisor.
L3: Remove Process.sleep from delete_device — in-flight jobs already
handle the race condition via verify_polling_assignment_unchanged.
The blocking sleep was unnecessary and delayed web requests by 500ms.
The :env config key IS properly set in all environments:
- config/test.exs:112 sets :test
- config/dev.exs:216 sets :dev
- config/runtime.exs:461 sets :prod
Application.get_env(:towerops, :env) works correctly at runtime.
