- Add _on_destroyed cleanup for global signal connections to prevent
  potential crashes after widget destruction
- Fix translation format bug in main_window.py (move .format() outside tr())
- Move prune signal connections from populate_from_profile() to __init__
  in archive_tab.py to prevent duplicate connections

Files with new cleanup handlers:
- networks_page.py, log_page.py, shell_commands_page.py

Files with extended cleanup handlers:
- repo_tab.py, source_tab.py, schedule_tab.py, schedule_page.py