Sort domains alphabetically

- GetAllDomains: order by name ASC
- GetUserAccessibleDomains: order by name ASC for both admin and regular users

backend/internal/api/handlers/users.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"log"
 	"net/http"
 	"strconv"
 
@@ -138,6 +139,7 @@ func (h *UserHandler) Create(c *gin.Context) {
 
 	user, err := h.db.CreateUserInDomain(req.Email, passwordHash, req.Quota, domain.ID)
 	if err != nil {
+		log.Printf("CreateUserInDomain error: email=%s, domain=%s, err=%v", req.Email, domainName, err)
 		Error(c, http.StatusInternalServerError, "failed to create user")
 		return
 	}