Translation Manager: diagnosed and fixed the v17.8.0 install bug

Translation Manager: tracked down why v17.8.0's core package shipped with unused ASP.NET Core Mvc/OpenApi references, breaking installs on some sites — root cause was a floating dotnet-version: "10.0.x" in release.yml resolving a different SDK patch on release day
pinned the exact .NET SDK via global.json, added packages.lock.json repo-wide for deterministic restores
found and fixed a separate footgun along the way: a local "Local" NuGet feed was shadowing nuget.org packages under identical version numbers with different content
verified with a throwaway v17.8.1-alpha01 prerelease, confirmed the published DLL was clean, then shipped v17.8.1 for real
updated the internal changelog and the customer-facing changelog/release on the companion Jumoo.TranslationManager.Issues repo