chore: delete dead progress handlers, no-op scar, split fused helper line

Batch H1 step 4:
- Handler GetUniversalProgress (progress.go) deleted — no route mounts
  it; only /api/progress/:id/history (GetProgressHistory) and the SSR
  /progress page exist. Note: the bruno universal-progress suite
  documents GET/PUT /api/progress/:id + /api/progress/device/:device_id
  — those routes do NOT exist server-side; that suite is stale
  documentation, flagged in the plan.
- Handler GetAllProgress deleted — unregistered near-copy of
  GetAllProgressData (which the /progress SSR page uses and stays).
- series.go: dropped the `_ = libTypes` no-op (libTypes IS used by the
  Badge line right below — the assignment stays).
- router/helpers.go: visibleLibraryIDsFor's signature and first
  statement were fused onto one line; split for readability. No
  behavior change.

internal/handlers/series.go

@@ -157,7 +157,6 @@ func (h *SeriesHandler) GetSeriesBooks(c *echo.Context) error {
 	for _, item := range books {
 		itemUUID, _ := uuid.FromBytes(item.ID.Bytes[0:16])
 		libTypes := LibraryTypeMap(c.Request().Context(), h.db)
-		_ = libTypes
 		bookCards = append(bookCards, BookInfo{
 			MediaItemID:    itemUUID.String(),
 			Title:          item.Title,