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.

docs/notify/samples/notify-event@1.sample.json

@@ -0,0 +1,34 @@
+{
+  "eventId": "8a8d6a2f-9315-49fe-9d52-8fec79ec7aeb",
+  "kind": "scanner.report.ready",
+  "version": "1",
+  "tenant": "tenant-01",
+  "ts": "2025-10-19T03:58:42+00:00",
+  "actor": "scanner-webservice",
+  "scope": {
+    "namespace": "prod-payment",
+    "repo": "ghcr.io/acme/api",
+    "digest": "sha256:79c1f9e5...",
+    "labels": {
+      "environment": "production"
+    },
+    "attributes": {}
+  },
+  "payload": {
+    "delta": {
+      "kev": [
+        "CVE-2025-40123"
+      ],
+      "newCritical": 1,
+      "newHigh": 2
+    },
+    "links": {
+      "rekor": "https://rekor.stella.local/api/v1/log/entries/1",
+      "ui": "https://ui.stella.local/reports/sha256-79c1f9e5"
+    },
+    "verdict": "fail"
+  },
+  "attributes": {
+    "correlationId": "scan-23a6"
+  }
+}