test(integration): F21 — docker-compose + env-driven SQL/LDAP harness mode

Adds a real-infra mode for the integration test harness alongside the default
in-memory mode. Drops the previously-untested code paths (EF SqlServer
behaviors, real LDAP bind) under env-var control without breaking the
zero-infra default that CI runs.

- docker-compose.yml — minimal SQL 2022 (14331) + OpenLDAP (3894) stack
  (ports chosen to coexist with docker-dev/ on 14330/3893)
- HarnessMode record reads OTOPCUA_HARNESS_USE_SQL=1 / USE_LDAP=1 from env
- SQL mode: per-harness unique DB OtOpcUa_Harness_{guid}, EnsureCreated
  at startup, EnsureDeleted on dispose (best-effort)
- LDAP mode: drops StubLdapAuthService and configures real LdapAuthService
  against the compose'd OpenLDAP via Authentication:Ldap:* config keys
- Microsoft.EntityFrameworkCore.SqlServer added to the test project
- README documents both modes + the macOS no-Docker caveat

Default in-memory mode unchanged — all 9 existing tests still pass.

tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests.csproj

@@ -13,6 +13,7 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk"/>
         <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing"/>
         <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory"/>
+        <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer"/>
         <PackageReference Include="Akka.Hosting"/>
         <PackageReference Include="xunit.runner.visualstudio">
             <PrivateAssets>all</PrivateAssets>