Tidy settings page layout

[wefalltomorrow]

Summary

Clean up the Settings page so controls no longer run into each other and the page reads clearly at different window sizes.

• Group exclusions, compression options, and display units into clear panels
• Use a responsive two-column settings layout that collapses to one column on narrower windows
• Keep labels, controls, and help text aligned instead of flowing inline
• Shorten and clarify the worker/thread help text
• Keep every existing setting and ID unchanged, so no configuration or JavaScript behavior changes

UI-only change; no compression/backend behavior is modified.