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/services/worker.go

@@ -73,8 +73,12 @@ func (j *Job) UpdateProgress(progress float64, filesScanned, newItems, errors in
 }
 
 type JobResult struct {
-	JobID        string      `json:"job_id"`
-	Status       JobStatus   `json:"status"`
+	JobID        string `json:"job_id"`
+	Status       JobStatus `json:"status"`
+	// LibraryID carries the scan job's library (from Params) so clients
+	// can label progress rows after a page refresh, when the original
+	// start-request context is gone.
+	LibraryID    string      `json:"library_id,omitempty"`
 	Error        string      `json:"error"`
 	Result       interface{} `json:"result"`
 	Progress     float64     `json:"progress"`
@@ -237,10 +241,12 @@ func (w *Worker) worker() {
 }
 
 func (w *Worker) processJob(job *Job) {
+	libID, _ := job.Params["library_id"].(string)
 	w.mu.Lock()
 	w.results[job.ID] = &JobResult{
-		JobID:  job.ID,
-		Status: JobStatusRunning,
+		JobID:     job.ID,
+		Status:    JobStatusRunning,
+		LibraryID: libID,
 	}
 	w.mu.Unlock()
 
@@ -313,8 +319,9 @@ func (w *Worker) processJob(job *Job) {
 	}
 
 	w.results[job.ID] = &JobResult{
-		JobID:  job.ID,
-		Status: status,
+		JobID:     job.ID,
+		Status:    status,
+		LibraryID: libID,
 		Error: func() string {
 			if err != nil {
 				return err.Error()
@@ -981,6 +988,23 @@ func (w *Worker) GetJobStatus(jobID string) (*JobResult, bool) {
 	return result, exists
 }
 
+// GetActiveScanJobs returns snapshots of every pending/running job.
+// Clients use it to re-attach to in-flight scans (e.g. after a page
+// refresh mid-scan) instead of only learning about scans from
+// websocket events.
+func (w *Worker) GetActiveScanJobs() []JobResult {
+	w.mu.RLock()
+	defer w.mu.RUnlock()
+
+	active := make([]JobResult, 0)
+	for _, result := range w.results {
+		if result.Status == JobStatusRunning || result.Status == JobStatusPending {
+			active = append(active, *result)
+		}
+	}
+	return active
+}
+
 func (w *Worker) CancelJob(jobID string) error {
 	w.mu.Lock()
 	defer w.mu.Unlock()