fix: installer checks containers only; the panel reads signed manifests from the registry when it has none; unsigned-updater nodes are labeled from the panel's manifests; sign node release images; release 0.3.0 [CI]

backend/tests/MoShiro.Backend.Tests/OwnerTests.cs

@@ -91,6 +91,9 @@ public sealed class OwnerEndToEndTests : IDisposable
             string script = await anonymous.GetStringAsync(path);
             Assert.Contains("MOSHIRO_ALLOW_NO_OWNER", script, StringComparison.Ordinal);
             Assert.Contains("this node has no owner", script, StringComparison.Ordinal);
+            // 只按容器判断「已经装过」：podman 的 inspect 不分类型，本机残留的旧镜像会被误当成已安装的容器
+            Assert.Contains("container inspect", script, StringComparison.Ordinal);
+            Assert.DoesNotContain("inspect \"$container\"", script.Replace("container inspect", ""), StringComparison.Ordinal);
         }
     }
 }