feat(transport): fleet-wide bundle-unlock throttle window (register row 52)

The per-IP unlock throttle's counters were a process-local ConcurrentDictionary
on each central node, so the effective fleet cap was N x
MaxUnlockAttemptsPerIpPerHour per client (failing over to the other node handed
the client a fresh budget) and a node restart cleared the window outright.

The window now lives in the central MS SQL BundleUnlockAttempt table — the HA
store both central nodes already share, so no new infrastructure, no new port,
no consensus protocol:

- Commons: BundleUnlockAttempt entity + IBundleUnlockAttemptRepository.
- ConfigurationDatabase: entity config (one index,
  IX_BundleUnlockAttempt_Client_Attempted, serving both the windowed count and
  the prune), repository (AsNoTracking count, ExecuteDeleteAsync prune),
  DbSet, DI registration, migration AddBundleUnlockAttemptTable + the
  hand-written idempotent production script under docs/plans/sql/.
- Transport: IBundleUnlockAttemptWindow seam + SqlBundleUnlockAttemptWindow
  (singleton; resolves the scoped repository from its own scope per call, like
  the central purge singletons). BundleUnlockRateLimiter keeps the policy and
  gains TryRegisterAttemptAsync; BundleImporter.LoadAsync calls it.

Behaviour preserved from row 44: locked bundles spend no hourly budget (the
lockout check still runs first), throttle denials burn no per-bundle strike and
are NOT recorded so they cannot roll the window forward, unattributable clients
share the stricter <unattributed> bucket, and the budget counts attempts rather
than failures. Config keys and their semantics are unchanged, so the rig's 500
override stays valid.

Three deliberate trades, documented in both Transport docs:
- FAILS OPEN. A store error logs a Warning naming the client and cap, and
  permits the attempt. This is a best-effort rate cap over an already
  authenticated, Administrator-gated surface — the availability of legitimate
  imports outranks the cap, and a DB blip must not make the import wizard
  unusable. Falling back to the process-local window was considered and
  rejected: it would still block a legitimate operator's 11th import.
- Approximate. Count-then-insert is not atomic across nodes, so simultaneous
  attempts can overshoot by the number in flight — bounded, self-correcting
  within the window, and not worth provider-specific raw SQL.
- Pruned opportunistically on the unlock path (CAS-claimed at most every 15
  min per process, bounded to 1000 rows, retaining 2x the window, best-effort
  try/catch) rather than by a new background service — Transport owns no
  central scheduler. Same shape as DeploymentService's terminal-record sweep.

Tests: Transport.IntegrationTests 116 passed (+10 — two limiter instances over
one store enforcing a single combined window, restart durability, denials
burning no budget, sliding release, bucket isolation, store-failure fail-open,
caller-cancellation not swallowed, no-shared-window fallback, prune and its
negative control); ConfigurationDatabase 395 passed (+5).

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

@@ -0,0 +1,28 @@
+namespace ZB.MOM.WW.ScadaBridge.Transport.Import;
+
+/// <summary>
+/// Register row 52: a sliding window of bundle-unlock attempts that is shared across the
+/// central pair, so <c>TransportOptions.MaxUnlockAttemptsPerIpPerHour</c> is a FLEET cap
+/// rather than a per-node, per-process one.
+/// <para>
+/// Implementations are expected to THROW on store failure. The fail-open decision belongs
+/// to <see cref="BundleUnlockRateLimiter"/>, which owns the policy (log a Warning and
+/// permit the attempt), not to the storage layer.
+/// </para>
+/// </summary>
+public interface IBundleUnlockAttemptWindow
+{
+    /// <summary>
+    /// Registers one unlock attempt against the shared window and reports whether it was
+    /// within budget. Implementations must NOT record an attempt they are rejecting —
+    /// a denial burns no budget, matching the in-memory limiter's contract (register
+    /// row 44), so a client that keeps hammering cannot extend its own lockout.
+    /// </summary>
+    /// <param name="clientKey">Throttle bucket — the caller's remote IP, or the shared unattributed bucket.</param>
+    /// <param name="maxAttemptsPerWindow">The trailing-window cap (<c>MaxUnlockAttemptsPerIpPerHour</c>).</param>
+    /// <param name="window">Trailing window the attempts are counted over (one hour in production).</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns><c>true</c> when the attempt was recorded (within budget); <c>false</c> when the bucket is exhausted.</returns>
+    Task<bool> TryRegisterAttemptAsync(
+        string clientKey, int maxAttemptsPerWindow, TimeSpan window, CancellationToken ct = default);
+}