Service: show the running version in the Service menu (so a self-update is visible)

Local checkpoint - NOT for public release. Answers "how will we know if the service
updated itself?"

- The service records its version + start time on every OnStart into ServiceStore
  (ProgramData). A self-update restart therefore bumps the version and refreshes the
  start time.
- The Service menu status line now shows it: "Service: installed, running — version 5.3,
  running since 2 min ago". So you can see the running version at a glance, and a recent
  start with a bumped version is the self-update landing.
- Also logged on start ("service: OnStart, version X") for the service log.

Status round-trip covered by the isolation self-test. Gate 27/27.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/SelfTest.cs

@@ -732,6 +732,10 @@ internal static class SelfTest
                 Check(back is not null && back.WasapiSendMode == "applications" && back.SelectedConnectedPeers.Contains("10.0.0.5"),
                     "the service profile must round-trip through the machine-wide store");
                 Check(ServiceStore.LoadLoggingEnabled(), "service logging flag must round-trip");
+
+                // Running status (version + start time) round-trips — this is what the Service menu shows.
+                ServiceStore.SaveStatus(new ServiceStore.ServiceStatus { Version = "5.3", StartedUtc = DateTime.UtcNow });
+                Check(ServiceStore.LoadStatus()?.Version == "5.3", "the service running-status version must round-trip");
             }
             finally { ServiceStore.TestDirectoryOverride = saved; }