fix(build): pin AngleSharp 1.5.2 to unbreak the solution build

GHSA-pgww-w46g-26qg (NU1902, moderate) on AngleSharp 1.1.1, pulled in
transitively by bunit into CentralUI.Tests. Under TreatWarningsAsErrors this
made `dotnet build ZB.MOM.WW.ScadaBridge.slnx` fail on a CLEAN main - the whole
suite was unbuildable and every "0 warnings / suite green" gate unverifiable.

Pre-existing, not introduced here; surfaced while starting LocalDb Phase 1,
whose per-task verification depends on a green baseline.

Same fix as the identical break in HistorianGateway (historiangw @ 6bc005d):
pin the leaf, test-only. AngleSharp is a bunit HTML-parsing dependency and
reaches no production project. Bumping bunit does not help - 2.0.33-preview is
the current preview line and still resolves the vulnerable AngleSharp.

Verified: dotnet build ZB.MOM.WW.ScadaBridge.slnx -> 0 Error(s), 0 Warning(s)
(was 1 Error before this commit).

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests.csproj

@@ -10,6 +10,9 @@
 
   <ItemGroup>
     <PackageReference Include="bunit" />
+    <!-- Security pin: GHSA-pgww-w46g-26qg. bunit pulls the vulnerable AngleSharp
+         1.1.1 transitively; 1.5.2 patches it. Test-only, no production reach. -->
+    <PackageReference Include="AngleSharp" />
     <PackageReference Include="coverlet.collector" />
     <PackageReference Include="Microsoft.AspNetCore.TestHost" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" />