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-template@1.sample.json

@@ -0,0 +1,19 @@
+{
+  "schemaVersion": "notify.template@1",
+  "templateId": "tmpl-slack-concise",
+  "tenantId": "tenant-01",
+  "channelType": "slack",
+  "key": "concise",
+  "locale": "en-us",
+  "body": "{{severity_icon payload.delta.newCritical}} {{summary}}",
+  "description": "Slack concise message for high severity findings.",
+  "renderMode": "markdown",
+  "format": "slack",
+  "metadata": {
+    "version": "2025-10-19"
+  },
+  "createdBy": "ops:zoya",
+  "createdAt": "2025-10-19T05:00:00+00:00",
+  "updatedBy": "ops:zoya",
+  "updatedAt": "2025-10-19T05:45:00+00:00"
+}