refactor: remove the runtime binary binding; every release registration path verifies the CI signature [CI]

The hash a node reports about itself cannot be trusted (a swapped binary can
copy the old hash), so the runtime binding only caught files that were replaced
by something that did not lie. Provenance stays where it can be verified: the
signed release manifest (digest) and the signed SHA256SUMS.

- Remove BinaryBindingService, the node_bindings table (schema v15 drops it),
  BinaryPolicy, the handshake hash/manifest fields and the admin binary column.
- Drop the per-platform "binaries" list from the release manifest, the hash
  scripts and the updater's installed.manifest copy.
- ReleaseService.PublishAsync now verifies the release signature, so the admin
  POST /releases route is no longer an unsigned path; tests sign with a test key.
- Docs: section 16 explains why the runtime check is gone.

backend/src/MoShiro.Backend.Api/Admin/BuildEndpoints.cs

@@ -25,9 +25,6 @@ public static class BuildEndpoints
         group.MapPost("/nodes/{id}/update", RequestUpdateAsync)
             .Api("nodes_update", "Ask an online agent or probe to install the release it has been offered", Tag).Returns<object>(StatusCodes.Status204NoContent).ProducesProblems(401, 403, 409)
             .Requires(Capability.UpdateConfirm);
-        group.MapDelete("/nodes/{id}/binary", ClearBinaryAsync)
-            .Api("nodes_binary_clear", "Accept the node's current binary: clear its binding so the next handshake binds it again", Tag).Returns<object>(StatusCodes.Status204NoContent).ProducesProblems(401, 403)
-            .Requires(Capability.FleetWrite);
         group.MapGet("/backend/update", BackendUpdateAsync)
             .Api("backend_update_get", "Current channel and host-verified backend update", Tag).Returns<BackendUpdateDto>().ProducesProblems(401, 403)
             .Requires(Capability.UpdateRead);
@@ -43,7 +40,7 @@ public static class BuildEndpoints
     public static void MapPublish(RouteGroupBuilder group)
     {
         group.MapPost("/releases", PublishReleaseAsync)
-            .Api("releases_publish", "Register a CI-signed release manifest; online nodes get it right away (their updaters verify the signature). Admin or release tokens", Tag)
+            .Api("releases_publish", "Register a CI-signed release manifest (the signature is checked against the release key); online nodes get it right away. Admin or release tokens", Tag)
             .Returns<ReleaseDto>(StatusCodes.Status201Created).ProducesProblems(400, 401, 403, 409)
             .Requires(Capability.ReleasePublish);
     }
@@ -60,12 +57,12 @@ public static class BuildEndpoints
             .Returns<ReleaseDto>(StatusCodes.Status201Created).ProducesProblems(400, 403, 409);
     }
 
-    private static async Task<IResult> OfferReleaseAsync(HttpContext http, ReleaseService releases, PublishReleaseRequest request)
+    private static async Task<IResult> OfferReleaseAsync(HttpContext http, ReleaseService releases, IReleaseKey releaseKey, PublishReleaseRequest request)
     {
         string manifest = request.Manifest ?? "";
         string signature = request.Signature ?? "";
         if (manifest.Length is 0 or > ReleaseService.MaxManifestBytes || signature.Length is 0 or > ReleaseService.MaxSignatureBytes
-            || !ReleaseSignature.Verify(InstallScripts.ReleaseKey(), manifest, signature))
+            || !ReleaseSignature.Verify(releaseKey.Pem, manifest, signature))
         {
             return Problems.Create(http, MoShiroErrors.Forbidden, "the manifest does not carry a valid release signature");
         }
@@ -73,14 +70,13 @@ public static class BuildEndpoints
         return await PublishReleaseAsync(http, releases, request);
     }
 
-    private static async Task<IResult> GetAsync(HttpContext http, NodeInfoService nodes, ReleaseService releases, BackendUpdates backendUpdates, BinaryBindingService bindings, NodeOwnerService owners, CancellationToken ct)
+    private static async Task<IResult> GetAsync(HttpContext http, NodeInfoService nodes, ReleaseService releases, BackendUpdates backendUpdates, NodeOwnerService owners, CancellationToken ct)
     {
         IReadOnlyDictionary<string, IReadOnlyList<NodeOwner>> ownerOf = await owners.ListAsync(ct);
-        Dictionary<string, NodeBinding> bound = (await bindings.ListAsync(ct)).ToDictionary(b => b.NodeId, StringComparer.Ordinal);
         var items = (await nodes.ListAsync(ct))
             .OrderBy(n => n.Kind, StringComparer.Ordinal)
             .ThenBy(n => n.NodeId, StringComparer.Ordinal)
-            .Select(n => new NodeBuildDto(n.NodeId, n.Kind, n.Os, n.OsName, n.Arch, n.Version, n.Tag, n.Commit, n.BuiltAt, ToDto(releases.StatusOf(new NodeId(n.NodeId))), bound.TryGetValue(n.NodeId, out NodeBinding? binding) ? ToDto(binding) : null, ownerOf.TryGetValue(n.NodeId, out IReadOnlyList<NodeOwner>? list) ? [.. list.Select(o => new NodeOwnerDto(o.CredentialId, o.PasskeyName, o.Username))] : null))
+            .Select(n => new NodeBuildDto(n.NodeId, n.Kind, n.Os, n.OsName, n.Arch, n.Version, n.Tag, n.Commit, n.BuiltAt, ToDto(releases.StatusOf(new NodeId(n.NodeId))), ownerOf.TryGetValue(n.NodeId, out IReadOnlyList<NodeOwner>? list) ? [.. list.Select(o => new NodeOwnerDto(o.CredentialId, o.PasskeyName, o.Username))] : null))
             .ToList();
         http.Response.Headers.CacheControl = "no-store";
         return TypedResults.Json(new BuildInfoDto(NodeEndpoints.Backend(withCommit: true), items, ToDto(await backendUpdates.GetAsync(ct))), ApiJsonContext.Default.BuildInfoDto);
@@ -138,17 +134,6 @@ public static class BuildEndpoints
         }
     }
 
-    private static NodeBinaryDto ToDto(NodeBinding b) =>
-        new(b.Sha256, b.Signed, b.Seq, DateTimeOffset.FromUnixTimeMilliseconds(b.BoundAtMs), b.Violation, b.ViolationAtMs is { } at ? DateTimeOffset.FromUnixTimeMilliseconds(at) : null);
-
-    /// <summary>管理员确认新的二进制是自己要的：清除绑定，节点下一次握手重新绑定（没有绑定可清也返回 204，幂等）。</summary>
-    private static async Task<IResult> ClearBinaryAsync(HttpContext http, BinaryBindingService bindings, string id)
-    {
-        http.SetDetail("binary binding cleared");
-        await bindings.ClearAsync(id, http.RequestAborted);
-        return TypedResults.NoContent();
-    }
-
     private static NodeUpdateDto? ToDto(UpdateStatus? status) =>
         status is null ? null : new NodeUpdateDto(status.State, status.Current, status.Available?.Tag, status.Available?.Version, status.Error, status.At > 0 ? DateTimeOffset.FromUnixTimeSeconds(status.At) : null);
 }

backend/src/MoShiro.Backend.Api/Contracts/AdminDtos.cs

@@ -185,13 +185,10 @@ public sealed record ChangePasswordRequest(string Password);
 public sealed record RecomputeDto(string State, IReadOnlyList<string> Metrics, long WindowsDone, long WindowsTotal, DateTimeOffset? From, DateTimeOffset? To, int QueueLength);
 
 /// <summary>管理端看的构建信息：每个节点自报的版本、tag、提交和构建时间，以及系统。</summary>
-/// <summary>节点二进制的绑定：第一次握手成功时绑定的 SHA-256。<c>Signed</c> 表示它出现在一份 CI 签名的清单里（否则只是首次握手时记下的）；<c>Violation</c> 是最近一次不符的原因，下一次握手符合了就清掉。</summary>
-public sealed record NodeBinaryDto(string Sha256, bool Signed, long Seq, DateTimeOffset BoundAt, string? Violation, DateTimeOffset? ViolationAt);
-
 /// <summary>节点的一个属主：节点报上来的（安装时固定在节点本地的）passkey 凭证 id，以及它在面板上对应的 passkey 名称和账户（对不上任何已注册的 passkey 时为空）。</summary>
 public sealed record NodeOwnerDto(string CredentialId, string? Passkey, string? Account);
 
-public sealed record NodeBuildDto(string Id, string Kind, string? Os, string? OsName, string? Arch, string? Version, string? Tag, string? Commit, string? BuiltAt, NodeUpdateDto? Update = null, NodeBinaryDto? Binary = null, IReadOnlyList<NodeOwnerDto>? Owners = null);
+public sealed record NodeBuildDto(string Id, string Kind, string? Os, string? OsName, string? Arch, string? Version, string? Tag, string? Commit, string? BuiltAt, NodeUpdateDto? Update = null, IReadOnlyList<NodeOwnerDto>? Owners = null);
 
 /// <summary>节点宿主机上的更新器报告的状态（<c>up_to_date</c>、<c>available</c>、<c>applying</c>、<c>failed</c>、<c>rolled_back</c>、<c>invalid</c>）；没装更新器的节点没有这个字段。</summary>
 public sealed record NodeUpdateDto(string State, string? CurrentDigest, string? AvailableTag, string? AvailableVersion, string? Error, DateTimeOffset? At);

backend/src/MoShiro.Backend.Api/Contracts/ApiJsonContext.cs

@@ -47,7 +47,6 @@ namespace MoShiro.Backend.Api;
 [JsonSerializable(typeof(PublishReleaseRequest))]
 [JsonSerializable(typeof(AboutDto))]
 [JsonSerializable(typeof(NodeBuildDto))]
-[JsonSerializable(typeof(NodeBinaryDto))]
 [JsonSerializable(typeof(NodeOwnerDto))]
 [JsonSerializable(typeof(BuildInfoDto))]
 [JsonSerializable(typeof(BackendUpdateDto))]