chore(transport): delete the dead BundleUnlockRateLimitedException

Superseded by BundleUnlockThrottledException when register row 44 wired the
limiter live and moved the typed exception to Commons so ManagementService's
MapFault could curate it. The original type has been unreferenced since —
never thrown, never caught, only its own definition — and with row 51 moving
BundleLockedException into the same Commons namespace there are now three
similarly-named unlock exceptions, one of which does nothing. A future
maintainer catching the dead one would silently get no coverage.

Solution builds clean with it gone (zero references). Transport 173 passed.

src/ZB.MOM.WW.ScadaBridge.Transport/Import/BundleUnlockRateLimitedException.cs

@@ -1,35 +0,0 @@
-namespace ZB.MOM.WW.ScadaBridge.Transport.Import;
-
-/// <summary>
-/// Thrown by <see cref="BundleImporter.LoadAsync"/> when the caller
-/// has exceeded the configured per-IP-per-hour unlock attempt cap
-/// (<see cref="TransportOptions.MaxUnlockAttemptsPerIpPerHour"/>). The 429-equivalent
-/// signal: the caller must wait for the trailing-hour window to roll forward before
-/// another passphrase attempt is accepted.
-/// </summary>
-public sealed class BundleUnlockRateLimitedException : Exception
-{
-    /// <summary>
-    /// Rate-limit key the limiter rejected the attempt against — the caller IP when
-    /// supplied, or the bundle's content hash as the architectural fallback (the
-    /// importer has no <c>IHttpContext</c> dependency by design).
-    /// </summary>
-    public string ClientKey { get; }
-
-    /// <summary>Per-window cap that was reached.</summary>
-    public int Limit { get; }
-
-    /// <summary>
-    /// Initializes a new <see cref="BundleUnlockRateLimitedException"/>.
-    /// </summary>
-    /// <param name="clientKey">The rate-limit key that exceeded its budget.</param>
-    /// <param name="limit">The configured per-window cap.</param>
-    public BundleUnlockRateLimitedException(string clientKey, int limit)
-        : base(
-            $"Bundle unlock rate limit reached ({limit} attempts per hour). "
-            + "Wait for the trailing-hour window to expire before retrying.")
-    {
-        ClientKey = clientKey ?? throw new ArgumentNullException(nameof(clientKey));
-        Limit = limit;
-    }
-}