feat: Initialize Zastava Webhook service with TLS and Authority authentication

- Added Program.cs to set up the web application with Serilog for logging, health check endpoints, and a placeholder admission endpoint.
- Configured Kestrel server to use TLS 1.3 and handle client certificates appropriately.
- Created StellaOps.Zastava.Webhook.csproj with necessary dependencies including Serilog and Polly.
- Documented tasks in TASKS.md for the Zastava Webhook project, outlining current work and exit criteria for each task.

src/StellaOps.Signer/StellaOps.Signer.Infrastructure/ServiceCollectionExtensions.cs

@@ -0,0 +1,24 @@
+using Microsoft.Extensions.DependencyInjection;
+using StellaOps.Signer.Core;
+using StellaOps.Signer.Infrastructure.Auditing;
+using StellaOps.Signer.Infrastructure.ProofOfEntitlement;
+using StellaOps.Signer.Infrastructure.Quotas;
+using StellaOps.Signer.Infrastructure.ReleaseVerification;
+using StellaOps.Signer.Infrastructure.Signing;
+
+namespace StellaOps.Signer.Infrastructure;
+
+public static class ServiceCollectionExtensions
+{
+    public static IServiceCollection AddSignerPipeline(this IServiceCollection services)
+    {
+        services.AddSingleton<ISignerPipeline, SignerPipeline>();
+        services.AddSingleton<IProofOfEntitlementIntrospector, InMemoryProofOfEntitlementIntrospector>();
+        services.AddSingleton<IReleaseIntegrityVerifier, DefaultReleaseIntegrityVerifier>();
+        services.AddSingleton<ISignerQuotaService, InMemoryQuotaService>();
+        services.AddSingleton<IDsseSigner, HmacDsseSigner>();
+        services.AddSingleton<ISignerAuditSink, InMemorySignerAuditSink>();
+        services.AddSingleton(TimeProvider.System);
+        return services;
+    }
+}