feat: operator trust root: passkey-signed operator set, signed join codes, nodes verify and pin the chain at enrollment [CI SKIP]

backend/src/MoShiro.Backend.Api/Common/Guards.cs

@@ -60,6 +60,9 @@ public static class PrincipalResolver
 /// </summary>
 public sealed record CapabilityRequirement(string? Capability);
 
+/// <summary>端点自己验 passkey 签名（见 <see cref="EndpointConventions.ElevationExempt"/>）。</summary>
+public sealed record ElevationExemptMarker;
+
 /// <summary>管理层守卫：按端点声明的能力授权；Cookie 会话的非 GET 请求必须带 <c>X-CSRF-Token</c>。</summary>
 public static class CapabilityGuard
 {
@@ -90,7 +93,7 @@ public static class CapabilityGuard
         }
 
         // 信任类的操作（加节点、吊销、改凭证）：登录用户还要有这一种的提权窗口；API key 自己带着能力，不经过这里
-        if (requirement.Capability is { } trusted && Elevation.For(trusted) is { } elevation && ElevationGate.Require(http, elevation, consume: true) is { } needed)
+        if (requirement.Capability is { } trusted && Elevation.For(trusted) is { } elevation && http.GetEndpoint()?.Metadata.GetMetadata<ElevationExemptMarker>() is null && ElevationGate.Require(http, elevation, consume: true) is { } needed)
         {
             return needed;
         }