chore(secrets): 0.4.0 — ship ZB.MOM.WW.Secrets.Replicator.Grpc (pull-only central hub)

Bumps the ZB.MOM.WW.Secrets family from 0.3.0 to 0.4.0 and adds the new
ZB.MOM.WW.Secrets.Replicator.Grpc package to the packable set. Publishes
all six 0.4.0 nupkgs to the dohertj2-gitea feed and restore-verifies the
new package resolves from it in a fresh --packages directory. Existing
packages are behaviorally unchanged — no breaking changes.

Adds ZB.MOM.WW.Secrets/CHANGELOG.md (none existed previously) to record
this and prior releases, and lists the new package in README.md's
Packages table. Also includes the controller's pending ledger updates
for docs/plans/2026-08-07-secrets-grpc-hub-implementation.md (Tasks
1-4 and 8 marked completed).

Claude-Session: https://claude.ai/code/session_014WNM4vjoVksyyBraTXSZE1

ZB.MOM.WW.Secrets/Directory.Build.props

@@ -5,7 +5,7 @@
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <LangVersion>latest</LangVersion>
-    <Version>0.3.0</Version>
+    <Version>0.4.0</Version>
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     <PackageReadmeFile>README.md</PackageReadmeFile>
   </PropertyGroup>