Split monolithic dashboard.js (2753 lines) into 18 focused modules
under dashboard/{core,data,ui,pages}/ with refresh.js and events.js
as orchestrators. Extracted ~900-line inline <style> into dashboard.css
and moved dashboard.html to dashboard/dashboard.html.
Split background.js (609 lines) into background/{logs,state,proxy,
native-messaging,tab-lifecycle,message-router}.js with a thin entry
point using importScripts().
Deleted dead files: wrong-domain.js (duplicate of inline script).
Updated manifest.json web_accessible_resources for new paths.
Updated docs/ARCHITECTURE.md to reflect the new file structure.
No functionality changed. No build step introduced.