feat: add service catalog management with policy integration for domain-based resource access control

Add ServiceCatalogItem type and services CRUD API endpoints (list, create, update, delete). Extend Policy type to include services array with domain, upstream_ip, proxy_ip, and ports metadata.

Add ServicesPage component with table view and create/edit modals for managing service definitions. Include service name, domain, proxy, and upstream columns with port parsing logic.

Integrate service selection

backend/internal/servicecatalog/handler.go

@@ -0,0 +1,78 @@
+package servicecatalog
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/google/uuid"
+
+	"nexavpn/backend/internal/apiutil"
+)
+
+type Handler struct {
+	service *CatalogService
+}
+
+func NewHandler(service *CatalogService) *Handler {
+	return &Handler{service: service}
+}
+
+func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
+	items, err := h.service.List(r.Context())
+	if err != nil {
+		apiutil.Error(w, http.StatusInternalServerError, "services_list_failed", "unable to list services")
+		return
+	}
+	apiutil.JSON(w, http.StatusOK, items)
+}
+
+func (h *Handler) Create(w http.ResponseWriter, r *http.Request) {
+	var input CreateRequest
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "invalid_json", "invalid request body")
+		return
+	}
+
+	item, err := h.service.Create(r.Context(), input)
+	if err != nil {
+		apiutil.Error(w, http.StatusInternalServerError, "service_create_failed", "unable to create service")
+		return
+	}
+	apiutil.JSON(w, http.StatusCreated, item)
+}
+
+func (h *Handler) Update(w http.ResponseWriter, r *http.Request) {
+	serviceID, err := uuid.Parse(chi.URLParam(r, "id"))
+	if err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "invalid_service_id", "invalid service id")
+		return
+	}
+
+	var input UpdateRequest
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "invalid_json", "invalid request body")
+		return
+	}
+
+	item, err := h.service.Update(r.Context(), serviceID, input)
+	if err != nil {
+		apiutil.Error(w, http.StatusInternalServerError, "service_update_failed", "unable to update service")
+		return
+	}
+	apiutil.JSON(w, http.StatusOK, item)
+}
+
+func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
+	serviceID, err := uuid.Parse(chi.URLParam(r, "id"))
+	if err != nil {
+		apiutil.Error(w, http.StatusBadRequest, "invalid_service_id", "invalid service id")
+		return
+	}
+
+	if err := h.service.Delete(r.Context(), serviceID); err != nil {
+		apiutil.Error(w, http.StatusInternalServerError, "service_delete_failed", "unable to delete service")
+		return
+	}
+	apiutil.JSON(w, http.StatusOK, map[string]any{"ok": true})
+}