10.0.0: Batch download with new background/content infrastructure, downloads UI, and a dedicated downloads page.

Added

• src/background/batch-download/* (state, runner, progress updates, tab cleanup).
• src/content/services/batch-download-service.ts + UI overlay and checkboxes.
• src/downloads/* (models, services, app, styles) and public/downloads.html.
• New shared components/buttons and batch-download-format enum.

Changed

• config-service, message-code, key-code, shortcut-type to support the new flow.
• downloads infrastructure across background + content.

Notes

• This release touches background/content/options/downloads at once.

Full Changelog: 9.0.0...10.0.0