build: bootstrap solution and quality gates (#3)

Closes #3

src/FinalFactory.Rendezvous.Server/Program.cs

@@ -0,0 +1,31 @@
+using System.Net;
+using FinalFactory.Rendezvous.Server.Transport;
+
+WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
+
+builder.Services
+    .AddOptions<UdpMediatorOptions>()
+    .BindConfiguration(UdpMediatorOptions.SectionName)
+    .ValidateDataAnnotations()
+    .Validate(
+        options => IPAddress.TryParse(options.ListenAddress, out _),
+        $"{UdpMediatorOptions.SectionName}:ListenAddress must be an IP address.")
+    .ValidateOnStart();
+builder.Services.AddSingleton<UdpMediatorService>();
+builder.Services.AddHostedService(static services => services.GetRequiredService<UdpMediatorService>());
+
+WebApplication app = builder.Build();
+
+app.MapGet("/health/live", static () => Results.Ok(new { status = "live" }));
+app.MapGet(
+    "/health/ready",
+    static (UdpMediatorService mediator) => mediator.LocalEndpoint is null
+        ? Results.StatusCode(StatusCodes.Status503ServiceUnavailable)
+        : Results.Ok(new { status = "ready" }));
+
+await app.RunAsync();
+
+/// <summary>
+/// Entry point marker used by integration-test hosts.
+/// </summary>
+public partial class Program;