feat(installer): harden database init and service setup steps

- InitDatabaseStep: create DbPath parent directory so custom paths work
- RegisterServiceStep: pass obj= argument so ServiceAccount is honoured
- StartServiceStep: poll for RUNNING state so downstream steps don't race

src/ClaudeDo.Installer/Steps/RegisterServiceStep.cs

@@ -43,13 +43,21 @@ public sealed class RegisterServiceStep : IInstallStep
 
         // Create service
         var startType = ctx.AutoStart ? "auto" : "demand";
-        var createArgs = $"create {ServiceName} binPath= \"{workerExe}\" start= {startType}";
 
         if (ctx.ServiceAccount == "CurrentUser")
             return StepResult.Fail(
                 "Service cannot run as Current User without a password. " +
                 "Select 'Local System' or extend ServicePage to capture a password.");
 
+        var objArg = ctx.ServiceAccount switch
+        {
+            "LocalSystem" => " obj= LocalSystem",
+            "NetworkService" => " obj= \"NT AUTHORITY\\NetworkService\"",
+            "LocalService" => " obj= \"NT AUTHORITY\\LocalService\"",
+            _ => "",
+        };
+        var createArgs = $"create {ServiceName} binPath= \"{workerExe}\" start= {startType}{objArg}";
+
         progress.Report("Creating service...");
         var (exitCode, output) = await RunSc(createArgs, ctx, progress, ct);
         if (exitCode == 1072)