feat: add ax serve command with JSON API backed by NodeService

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

service/config.go

@@ -6,6 +6,11 @@ type Alias struct {
 	Description string `json:"description,omitempty"`
 }
 
+type ServerConfig struct {
+	Host string `json:"host"`
+	Port int    `json:"port"`
+}
+
 type Config interface {
 	GetUser() string
 	SetUser(username string) error
@@ -13,5 +18,6 @@ type Config interface {
 	SetAlias(alias *Alias) error
 	DeleteAlias(name string) error
 	ListAliases() ([]*Alias, error)
+	GetServerConfig() ServerConfig
 	Save() error
 }