fix(transport): drop the external-definition lookup cache after a committed bundle import (ScadaBridge#83)

The bundle importer writes external systems, methods and database connections
through the raw DbContext, bypassing the ManagementActor handlers that
invalidate ExternalDefinitionLookupCache (#65), so the importing node served
pre-import definitions for up to DefinitionCacheTtl. New Commons seam
IExternalDefinitionCacheInvalidator, implemented by the cache and registered as
the same singleton; BundleImporter takes it optionally and invalidates once
after every committed import (never on rollback; never throws).

Peer-central-node invalidation (the other half of #83) is NOT done here: the
issue leaves open whether the 10 s TTL bound is acceptable for the peer.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Services/IExternalDefinitionCacheInvalidator.cs

@@ -0,0 +1,15 @@
+namespace ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
+
+/// <summary>
+/// Drops the node-local cache of external-system / method / database-connection definitions
+/// (<c>ExternalSystemGateway.ExternalDefinitionLookupCache</c>) after a committed write to
+/// those definitions, so the editing node serves the new definition immediately instead of
+/// after the cache TTL. Lives in Commons so a writer that cannot reference the gateway (the
+/// Transport bundle importer, Gitea #83) can still signal it. Scope is THIS node only — a
+/// peer central node converges within the TTL.
+/// </summary>
+public interface IExternalDefinitionCacheInvalidator
+{
+    /// <summary>Drops every cached definition on this node.</summary>
+    void InvalidateAll();
+}