feat(rate-limiting): Implement core rate limiting functionality with configuration, decision-making, metrics, middleware, and service registration

- Add RateLimitConfig for configuration management with YAML binding support.
- Introduce RateLimitDecision to encapsulate the result of rate limit checks.
- Implement RateLimitMetrics for OpenTelemetry metrics tracking.
- Create RateLimitMiddleware for enforcing rate limits on incoming requests.
- Develop RateLimitService to orchestrate instance and environment rate limit checks.
- Add RateLimitServiceCollectionExtensions for dependency injection registration.

src/Signer/StellaOps.Signer/StellaOps.Signer.Tests/StellaOps.Signer.Tests.csproj

@@ -11,6 +11,7 @@
   <ItemGroup>
     <PackageReference Include="BouncyCastle.Cryptography" Version="2.6.2" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.0" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="10.0.0-preview.7.24407.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.0" />
     <PackageReference Include="xunit" Version="2.9.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
@@ -22,6 +23,7 @@
     <ProjectReference Include="..\StellaOps.Signer.WebService\StellaOps.Signer.WebService.csproj" />
     <ProjectReference Include="..\StellaOps.Signer.Infrastructure\StellaOps.Signer.Infrastructure.csproj" />
     <ProjectReference Include="..\StellaOps.Signer.Core\StellaOps.Signer.Core.csproj" />
+    <ProjectReference Include="..\..\__Libraries\StellaOps.Signer.KeyManagement\StellaOps.Signer.KeyManagement.csproj" />
     <ProjectReference Include="../../../__Libraries/StellaOps.Configuration/StellaOps.Configuration.csproj" />
     <ProjectReference Include="../../../__Libraries/StellaOps.DependencyInjection/StellaOps.DependencyInjection.csproj" />
     <ProjectReference Include="../../../__Libraries/StellaOps.Cryptography/StellaOps.Cryptography.csproj" />