Users reported slow download speeds from the default Kiwix CDN. This adds
the ability to browse and download ZIM files from alternative Kiwix mirrors
or self-hosted repositories, all through the GUI.
- Add "Custom Libraries" button next to "Browse the Kiwix Library"
- Source dropdown to switch between Default (Kiwix) and custom libraries
- Browsable directory structure with breadcrumb navigation
- 5 pre-seeded official Kiwix mirrors (US, DE, DK, UK, Global CDN)
- Built-in mirrors protected from deletion
- Downloads use existing pipeline (progress, cancel, Kiwix restart)
- Source selection persists across page loads via localStorage
- Scrollable directory browser (600px max) with sticky header
- SSRF protection on all custom library URLs
Closes#576
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
