wire time_format into scope, add settings UI selector, change defaults to 24h, and replace all user-facing Calendar.strftime calls with centralized TimeHelpers using the user's timezone and time format.
Completes the flash message migration by converting all remaining user-facing strings: **UserAuth.ex changes:** - All Plug functions: require_sudo_mode, require_authenticated_user, require_superuser - load_current_organization error messages (3 messages) - All LiveView on_mount callbacks (8 auth-related messages) - Policy consent success message **SessionManager.ex changes:** - Mobile device session management (2 messages) - Alert preferences updates (3 messages including conditional) All messages now use t_auth() for consistent translation in the auth domain. All tests passing (100 tests).
