Add manifest.json with app metadata, theme colors, and icon configuration for installable PWA. Add service worker (sw.js) with shell caching strategy for offline support - caches static assets on install, cleans old caches on activate, and implements network-first fetch with cache fallback for non-API requests.
Update index.html with PWA meta tags (theme-color, mobile
Add parse_size_bytes() and format_bytes() helper functions to convert and format file sizes. Calculate total remaining bytes from queue and include active_count, history_count, remaining_bytes, and formatted remaining in downloads API response. Update error responses to include new fields.
Add media-mark.svg favicon with gradient background, golden lines, and green checkmark. Replace text logo with inline