refactor(vis): H4.5 step 2 — series endpoints on the canonical resolver

Series' visibleLibrarySet was the third hand-rolled set builder (with
its own FromBytes-error idiom, the fourth idiom in four copies).
SeriesService.VisibleLibraries — a pure pass-through to
GetUserVisibleLibraries — now has zero callers and dies with the
migration.

internal/handlers/series.go

@@ -13,14 +13,16 @@ import (
 )
 
 type SeriesHandler struct {
-	seriesService *services.SeriesService
-	db            *database.Queries
+	seriesService  *services.SeriesService
+	libraryService *services.LibraryService
+	db             *database.Queries
 }
 
 func NewSeriesHandler(db *database.Queries) *SeriesHandler {
 	return &SeriesHandler{
-		seriesService: services.NewSeriesService(db),
-		db:            db,
+		seriesService:  services.NewSeriesService(db),
+		libraryService: services.NewLibraryService(db),
+		db:             db,
 	}
 }
 
@@ -104,24 +106,7 @@ func (h *SeriesHandler) visibleLibrarySet(c *echo.Context) (map[string]bool, []p
 	if !ok {
 		return nil, nil, echo.NewHTTPError(http.StatusUnauthorized, "invalid user")
 	}
-	libraries, err := h.seriesService.VisibleLibraries(c.Request().Context(), user.ID)
-	if err != nil {
-		return nil, nil, echo.NewHTTPError(http.StatusInternalServerError, "failed to check library access")
-	}
-	set := make(map[string]bool, len(libraries))
-	ids := make([]pgtype.UUID, 0, len(libraries))
-	for _, lib := range libraries {
-		if !lib.ID.Valid {
-			continue
-		}
-		libUUID, err := uuid.FromBytes(lib.ID.Bytes[0:16])
-		if err != nil {
-			continue
-		}
-		set[libUUID.String()] = true
-		ids = append(ids, lib.ID)
-	}
-	return set, ids, nil
+	return h.libraryService.VisibleLibrarySet(c.Request().Context(), user.ID)
 }
 
 func (h *SeriesHandler) GetSeriesBooks(c *echo.Context) error {