fix(admin): authenticate SignalR hub clients with a bearer-token scheme

The Admin-003 fix gated every SignalR hub with [Authorize], but the server-side
Blazor HubConnection clients had no way to authenticate: the browser's HttpOnly
auth cookie is not reachable from the interactive circuit, so every hub negotiate
returned 401 and the Admin live-update feature was non-functional app-wide
(silently degraded on Hosts/ScriptLog, fatal on the cluster pages).

Introduce a token-based hub auth path:
- HubTokenService mints/validates short-lived tokens using ASP.NET Core Data
  Protection (the same primitive that protects the auth cookie — no signing-key
  management, no new packages). Tokens carry the user's name + roles.
- HubTokenAuthenticationHandler is a custom "HubToken" auth scheme that reads the
  token from the Authorization: Bearer header (negotiate) or the access_token
  query parameter (WebSocket upgrade).
- The "HubClients" authorization policy runs both the cookie and HubToken
  schemes; the hub endpoints use RequireAuthorization("HubClients").
- AdminHubConnectionFactory builds hub connections with an AccessTokenProvider
  that mints a fresh token for the circuit's authenticated user on every
  (re)connect. All six hub-consuming pages now resolve connections through it.

Hub negotiate now returns 200 and the WebSocket upgrades (101); live updates
work. The best-effort try/catch guards added previously are kept as defence.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Server/ZB.MOM.WW.OtOpcUa.Admin/Security/HubTokenAuthenticationHandler.cs

@@ -0,0 +1,58 @@
+using System.Text.Encodings.Web;
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.Extensions.Options;
+
+namespace ZB.MOM.WW.OtOpcUa.Admin.Security;
+
+/// <summary>Scheme name for the SignalR hub bearer-token authentication.</summary>
+public static class HubTokenDefaults
+{
+    public const string AuthenticationScheme = "HubToken";
+}
+
+/// <summary>
+///     Authenticates SignalR hub requests that carry a <see cref="HubTokenService"/>-minted
+///     token. SignalR supplies the token as an <c>Authorization: Bearer</c> header on the
+///     negotiate / long-poll requests and as an <c>access_token</c> query-string parameter on
+///     the WebSocket upgrade (custom headers cannot be set on a browser WebSocket handshake) —
+///     this handler accepts either.
+/// </summary>
+public sealed class HubTokenAuthenticationHandler : AuthenticationHandler<AuthenticationSchemeOptions>
+{
+    private readonly HubTokenService _tokens;
+
+    public HubTokenAuthenticationHandler(
+        IOptionsMonitor<AuthenticationSchemeOptions> options,
+        ILoggerFactory logger,
+        UrlEncoder encoder,
+        HubTokenService tokens)
+        : base(options, logger, encoder)
+    {
+        _tokens = tokens;
+    }
+
+    protected override Task<AuthenticateResult> HandleAuthenticateAsync()
+    {
+        var token = ExtractToken();
+        if (string.IsNullOrEmpty(token))
+            return Task.FromResult(AuthenticateResult.NoResult());
+
+        var principal = _tokens.Validate(token);
+        if (principal is null)
+            return Task.FromResult(AuthenticateResult.Fail("Invalid or expired hub token."));
+
+        return Task.FromResult(AuthenticateResult.Success(
+            new AuthenticationTicket(principal, Scheme.Name)));
+    }
+
+    private string? ExtractToken()
+    {
+        var header = Request.Headers.Authorization.ToString();
+        if (header.StartsWith("Bearer ", StringComparison.OrdinalIgnoreCase))
+            return header["Bearer ".Length..].Trim();
+
+        return Request.Query.TryGetValue("access_token", out var queryToken)
+            ? queryToken.ToString()
+            : null;
+    }
+}

src/Server/ZB.MOM.WW.OtOpcUa.Admin/Security/HubTokenService.cs

@@ -0,0 +1,79 @@
+using System.Security.Claims;
+using System.Text.Json;
+using Microsoft.AspNetCore.DataProtection;
+
+namespace ZB.MOM.WW.OtOpcUa.Admin.Security;
+
+/// <summary>
+///     Mints and validates short-lived bearer tokens that let the Admin UI's server-side
+///     Blazor <see cref="Microsoft.AspNetCore.SignalR.Client.HubConnection"/> clients
+///     authenticate to the <c>[Authorize]</c>-gated SignalR hubs.
+/// </summary>
+/// <remarks>
+///     The Admin-003 fix gated every hub with authorization, but a server-side Blazor circuit
+///     cannot forward the browser's HttpOnly auth cookie to the loopback hub connection — so the
+///     hub negotiate would 401. Instead, a component mints a token here for its already-
+///     authenticated user and supplies it through <c>HttpConnectionOptions.AccessTokenProvider</c>;
+///     <see cref="HubTokenAuthenticationHandler"/> validates it on the hub endpoint.
+///     <para>
+///         The token is an ASP.NET Core Data Protection time-limited payload — the same
+///         primitive that already protects the auth cookie — so there is no signing-key
+///         management and no extra package. It is only ever presented loopback (the Admin
+///         server connecting to its own hub).
+///     </para>
+/// </remarks>
+public sealed class HubTokenService
+{
+    private const string ProtectorPurpose = "ZB.MOM.WW.OtOpcUa.Admin.HubToken.v1";
+    private static readonly TimeSpan TokenLifetime = TimeSpan.FromMinutes(30);
+
+    private readonly ITimeLimitedDataProtector _protector;
+
+    public HubTokenService(IDataProtectionProvider dataProtection)
+    {
+        _protector = dataProtection.CreateProtector(ProtectorPurpose).ToTimeLimitedDataProtector();
+    }
+
+    /// <summary>Mints a token carrying the user's name and roles, valid for 30 minutes.</summary>
+    public string Issue(ClaimsPrincipal user)
+    {
+        var payload = new HubTokenPayload(
+            user.Identity?.Name,
+            user.FindFirstValue(ClaimTypes.NameIdentifier),
+            user.FindAll(ClaimTypes.Role).Select(c => c.Value).ToArray());
+        return _protector.Protect(JsonSerializer.Serialize(payload), TokenLifetime);
+    }
+
+    /// <summary>
+    ///     Validates a token and rebuilds the <see cref="ClaimsPrincipal"/>. Returns
+    ///     <c>null</c> when the token is missing, tampered with, or expired.
+    /// </summary>
+    public ClaimsPrincipal? Validate(string? token)
+    {
+        if (string.IsNullOrEmpty(token)) return null;
+
+        try
+        {
+            var payload = JsonSerializer.Deserialize<HubTokenPayload>(_protector.Unprotect(token));
+            if (payload is null) return null;
+
+            var claims = new List<Claim>();
+            if (!string.IsNullOrEmpty(payload.Name))
+                claims.Add(new Claim(ClaimTypes.Name, payload.Name));
+            if (!string.IsNullOrEmpty(payload.NameIdentifier))
+                claims.Add(new Claim(ClaimTypes.NameIdentifier, payload.NameIdentifier));
+            claims.AddRange((payload.Roles ?? []).Select(r => new Claim(ClaimTypes.Role, r)));
+
+            var identity = new ClaimsIdentity(
+                claims, HubTokenDefaults.AuthenticationScheme, ClaimTypes.Name, ClaimTypes.Role);
+            return new ClaimsPrincipal(identity);
+        }
+        catch
+        {
+            // Crypto failure (tampered / expired / wrong key) or malformed JSON — unauthenticated.
+            return null;
+        }
+    }
+
+    private sealed record HubTokenPayload(string? Name, string? NameIdentifier, string[]? Roles);
+}