Bug: the admin 'Scanning Libraries' widget fed the server's 0-1
progress straight into percent strings and bar widths, so the overall
and per-library percentages capped at '1%' and the bars never filled.
Both now scale by 100 (matching the setup page, which was already
correct).
Bug: scan state only reached clients via websocket events, so a page
opened (or refreshed) mid-scan showed nothing until the next tick —
and the admin widget never re-attached at all. The worker now exposes
active jobs (with their library_id so rows keep their names), served
as GET /api/scanner/active (admin, re-attaches the widget + polling)
and GET /api/scanner/active-summary (any user, restores the sidebar
indicator on load). Idle hides both, exactly as before.
Annoyance: the sidebar's 'Scanning… N%' was a block element between
the logo and the nav, shoving every menu entry down while a scan ran.
The percent now lives inside the fixed-height logo row next to the
spinner (spinner last, so growing digits extend leftward); nothing
below it moves.
