feat: Implement DefaultCryptoHmac for compliance-aware HMAC operations

- Added DefaultCryptoHmac class implementing ICryptoHmac interface.
- Introduced purpose-based HMAC computation methods.
- Implemented verification methods for HMACs with constant-time comparison.
- Created HmacAlgorithms and HmacPurpose classes for well-known identifiers.
- Added compliance profile support for HMAC algorithms.
- Included asynchronous methods for HMAC computation from streams.

docs/risk/samples/factors/SHA256SUMS

@@ -0,0 +1,2 @@
+5b7eee78aed1ee13378737c35cd2b5e91aa4abbbd0e70029219d5e357b40ab1f  README.md
+13cf45be5a287a38d000aff4db266616e765fc1acdc1df9f37b2e03eb729d1d2  factors-normalized.json

docs/risk/samples/factors/factors-normalized.json

@@ -0,0 +1,44 @@
+{
+  "profile_id": "default-profile",
+  "context_id": "ctx-001",
+  "factors": [
+    {
+      "name": "cvss",
+      "source": "nvd",
+      "type": "numeric",
+      "path": "/cvss/base_score",
+      "raw_value": 7.5,
+      "normalized_value": 0.75,
+      "weight": 0.4,
+      "contribution": 0.4,
+      "timestamp_utc": "2025-12-05T00:00:00Z",
+      "provenance": "sha256:cvsshash"
+    },
+    {
+      "name": "kev",
+      "source": "cisa",
+      "type": "boolean",
+      "path": "/kev/in_catalog",
+      "raw_value": true,
+      "normalized_value": 1.0,
+      "weight": 0.3,
+      "contribution": 0.3,
+      "timestamp_utc": "2025-12-05T00:00:00Z",
+      "provenance": "sha256:kevhash"
+    },
+    {
+      "name": "reachability",
+      "source": "scanner",
+      "type": "numeric",
+      "path": "/reachability/score",
+      "raw_value": 0.9,
+      "normalized_value": 0.9,
+      "weight": 0.3,
+      "contribution": 0.3,
+      "timestamp_utc": "2025-12-05T00:00:01Z",
+      "provenance": "sha256:reachhash"
+    }
+  ],
+  "ordering": "factor_type->source->timestamp_utc",
+  "precision": 4
+}