- Add usePageVisibility hook to track page visibility state - Add pauseWhenHidden option to usePolledData (defaults to false for backward compatibility) - When enabled, polling pauses when page is hidden and resumes with immediate refresh when visible - Refactor useBlocklistStatus to use usePolledData with pauseWhenHidden=true - Add comprehensive tests for usePageVisibility hook - Add polling lifecycle documentation to Web-Development.md Fixes #36: Polling continues when tab is not visible Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>