fix(backend): dbErr 503 degradation for connection-class DB errors

backend/internal/api/libraries.go

@@ -3,7 +3,6 @@ package api
 import (
 	"context"
 	"io"
-	"log"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -31,8 +30,7 @@ func (a *api) libRoot(c *gin.Context, lib store.Library) (string, bool) {
 func (a *api) listLibraries(c *gin.Context) {
 	libs, e := a.st.ListLibraries(c)
 	if e != nil {
-		log.Printf("db: %v", e)
-		err(c, http.StatusInternalServerError, "internal", "db error")
+		dbErr(c, e)
 		return
 	}
 	out := make([]gin.H, 0, len(libs))