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/events/scanner.report.ready@1.json

@@ -21,14 +21,28 @@
       "type": "object",
       "required": ["verdict", "delta", "links"],
       "properties": {
+        "reportId": {"type": "string"},
+        "generatedAt": {"type": "string", "format": "date-time"},
         "verdict": {"enum": ["pass", "warn", "fail"]},
+        "summary": {
+          "type": "object",
+          "properties": {
+            "total": {"type": "integer", "minimum": 0},
+            "blocked": {"type": "integer", "minimum": 0},
+            "warned": {"type": "integer", "minimum": 0},
+            "ignored": {"type": "integer", "minimum": 0},
+            "quieted": {"type": "integer", "minimum": 0}
+          },
+          "additionalProperties": false
+        },
         "delta": {
           "type": "object",
           "properties": {
             "newCritical": {"type": "integer", "minimum": 0},
             "newHigh": {"type": "integer", "minimum": 0},
             "kev": {"type": "array", "items": {"type": "string"}}
-          }
+          },
+          "additionalProperties": false
         },
         "links": {
           "type": "object",
@@ -37,6 +51,30 @@
             "rekor": {"type": "string", "format": "uri"}
           },
           "additionalProperties": false
+        },
+        "quietedFindingCount": {"type": "integer", "minimum": 0},
+        "report": {"type": "object"},
+        "dsse": {
+          "type": "object",
+          "required": ["payloadType", "payload", "signatures"],
+          "properties": {
+            "payloadType": {"type": "string"},
+            "payload": {"type": "string"},
+            "signatures": {
+              "type": "array",
+              "items": {
+                "type": "object",
+                "required": ["keyId", "algorithm", "signature"],
+                "properties": {
+                  "keyId": {"type": "string"},
+                  "algorithm": {"type": "string"},
+                  "signature": {"type": "string"}
+                },
+                "additionalProperties": false
+              }
+            }
+          },
+          "additionalProperties": false
         }
       },
       "additionalProperties": true