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.Scanner.WebService/Contracts/PolicyDiagnosticsContracts.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace StellaOps.Scanner.WebService.Contracts;
+
+public sealed record PolicyDiagnosticsRequestDto
+{
+    [JsonPropertyName("policy")]
+    public PolicyPreviewPolicyDto? Policy { get; init; }
+}
+
+public sealed record PolicyDiagnosticsResponseDto
+{
+    [JsonPropertyName("success")]
+    public bool Success { get; init; }
+
+    [JsonPropertyName("version")]
+    public string Version { get; init; } = string.Empty;
+
+    [JsonPropertyName("ruleCount")]
+    public int RuleCount { get; init; }
+
+    [JsonPropertyName("errorCount")]
+    public int ErrorCount { get; init; }
+
+    [JsonPropertyName("warningCount")]
+    public int WarningCount { get; init; }
+
+    [JsonPropertyName("generatedAt")]
+    public DateTimeOffset GeneratedAt { get; init; }
+
+    [JsonPropertyName("issues")]
+    public IReadOnlyList<PolicyPreviewIssueDto> Issues { get; init; } = Array.Empty<PolicyPreviewIssueDto>();
+
+    [JsonPropertyName("recommendations")]
+    public IReadOnlyList<string> Recommendations { get; init; } = Array.Empty<string>();
+}