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.ConfigurationDatabase/Configurations/BundleUnlockAttemptEntityTypeConfiguration.cs

@@ -0,0 +1,46 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Transport;
+
+namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Configurations;
+
+/// <summary>
+/// Maps the <see cref="BundleUnlockAttempt"/> POCO to the central
+/// <c>BundleUnlockAttempt</c> table — the fleet-wide sliding window behind the Transport
+/// component's per-client bundle-unlock throttle (register row 52). Operational history,
+/// NOT audit, so the table is non-partitioned, standard <c>[PRIMARY]</c> filegroup, no
+/// DB-role restriction.
+/// </summary>
+/// <remarks>
+/// One named index, <c>IX_BundleUnlockAttempt_Client_Attempted</c>, serves both access
+/// paths: the window count seeks on <c>ClientKey</c> and ranges on
+/// <c>AttemptedAtUtc</c>, and the opportunistic prune scans the same index by time. A
+/// second time-only index was deliberately not added — the table is kept small by the
+/// prune, so the leading-column seek is cheap enough for the prune to share.
+/// </remarks>
+public class BundleUnlockAttemptEntityTypeConfiguration : IEntityTypeConfiguration<BundleUnlockAttempt>
+{
+    /// <summary>
+    /// Configures the EF Core entity type mapping for <see cref="BundleUnlockAttempt"/>.
+    /// </summary>
+    /// <param name="builder">The entity type builder to configure.</param>
+    public void Configure(EntityTypeBuilder<BundleUnlockAttempt> builder)
+    {
+        builder.ToTable("BundleUnlockAttempt");
+
+        // Surrogate long identity assigned by the store.
+        builder.HasKey(a => a.Id);
+
+        // Bucket key: an IP literal or the "<unattributed>" sentinel. 64 chars covers an
+        // IPv6 address with a scope id; ASCII, so non-unicode (varchar) like every other
+        // catalog-bounded column in the schema.
+        builder.Property(a => a.ClientKey).HasMaxLength(64).IsUnicode(false).IsRequired();
+
+        builder.Property(a => a.AttemptedAtUtc).IsRequired();
+
+        // Window index — seeks the bucket, ranges over the trailing hour, and is
+        // reused by the prune's time scan. Name locked for migration discoverability.
+        builder.HasIndex(a => new { a.ClientKey, a.AttemptedAtUtc })
+            .HasDatabaseName("IX_BundleUnlockAttempt_Client_Attempted");
+    }
+}