feat(all): add game SDK and harden client login and game rules

- Add costume burst upgrades with durable replay and fix permanent SR equipment gacha.
- Add server game.json rules for optional collaboration UR weapons, with packaging and documentation.
- Add GameNames/GameSdk NuGet tooling, readable types, reobfuscation, complete source/PDB navigation and shared-runtime installation.
- Split plugin responsibilities, prefer typeof/nameof, centralize MSBuild settings and ignore local paths; remove the unused LoginUI test project.
- Fix login recovery and TLS through native platform HTTP and a private game relay; read device region directly from the OS time zone.

Validation: go test ./... -count=1, go vet ./..., plugin Release builds, SDK/runtime self-tests, Roslyn embedded-source navigation, gofmt check and git diff --check.

plugins/GameSdk/samples/ExamplePlugin/ExamplePlugin.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netstandard2.1</TargetFramework>
+    <LangVersion>latest</LangVersion>
+    <AssemblyName>ExamplePlugin</AssemblyName>
+    <!-- GameDir belongs in local Directory.Build.props or on the command line. -->
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="BD2.GameSdk" Version="0.2.1-game.2.35.10" PrivateAssets="all" />
+  </ItemGroup>
+</Project>