feat: add getOutboundGateway effect and simplify VersionGraph init/uninit

Add getOutboundGateway effect across core, container-runtime, and SDK
to let services query their effective outbound gateway with callback
support. Remove preInstall/uninstall hooks from VersionGraph as they
are no longer needed.

sdk/base/lib/Effects.ts

@@ -135,6 +135,8 @@ export type Effects = {
   }): Promise<string>
   /** Returns the IP address of StartOS */
   getOsIp(): Promise<string>
+  /** Returns the effective outbound gateway for this service */
+  getOutboundGateway(options: { callback?: () => void }): Promise<string>
   // interface
   /** Creates an interface bound to a specific host and port to show to the user */
   exportServiceInterface(options: ExportServiceInterfaceParams): Promise<null>