refactor: remove service factory wrappers, call store init methods directly

Replace InitNodeService/GetNodeService/GetNodeServiceForUser with thin
NewLocalNodeService/NewRemoteNodeService constructors; move wiring logic
into cmd/root.go (getNodeService helper) and an inline closure in serve.go.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/cmd/add.go

@@ -15,7 +15,7 @@ var cTags, cRels []string
 var addCmd = &cobra.Command{
 	Use: "add <title>", Short: "Create a new node", Args: cobra.ExactArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
-		svc, err := service.GetNodeService(cfg)
+		svc, err := getNodeService()
 		if err != nil {
 			fmt.Fprintln(os.Stderr, err)
 			return