fix(web): scan progress — correct percentages, no layout shift, refresh-survivable

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.

internal/router/router.go

@@ -332,9 +332,9 @@ func RegisterRoutes(cfg *Config) *handlers.Handler {
 	// Register progress routes with actual handler
 	registerProgressRoutes(cfg, scannerHandler)
 
-	// Register scanner routes (admin only)
+	// Register scanner routes (admin only, plus the sitewide summary)
 	admin := protected.Group("", handlers.AdminMiddleware)
-	registerScannerRoutes(admin, scannerHandler)
+	registerScannerRoutes(protected, admin, scannerHandler)
 
 	// Hash conflict routes (admin only)
 	admin.GET("/api/admin/hash-conflicts", cfg.HashConflictsHandler.ListHashConflicts)