Enhance risk API documentation and error handling

- Updated API documentation for risk endpoints to include optional caching headers and error catalog references.
- Added a new error catalog JSON file to standardize error responses.
- Improved explainability documentation with sample outputs for console and CLI.
- Added SHA256 checksums for new sample files related to explainability.
- Refined AocGuard tests to utilize a helper method for generating test JSON, improving readability and maintainability.
- Updated runbook references to ensure consistency in sprint documentation.
- Introduced stub implementations for MongoDB storage interfaces and options, laying groundwork for future development.
- Disabled analytics in Angular CLI configuration for privacy considerations.

docs/risk/samples/explain/cli-explain.txt

@@ -0,0 +1,12 @@
+stella risk explain job-001 --tenant tenant-default --json false
+Finding: finding-123
+Profile: default-profile v1.0.0 (hash sha256:profilehash)
+Score: 0.85 (high)
+Gates: kev_and_reachability
+Contributions:
+- cvss          0.40 (raw 7.5, source nvd, provenance sha256:cvsshash)
+- kev           0.30 (raw true, source cisa, provenance sha256:kevhash)
+- reachability  0.30 (raw 0.9, source scanner, provenance sha256:reachhash)
+Overrides: kev-boost (Known Exploited Vulnerability)
+Provenance: job sha256:jobhash | fixtures [sha256:cvsshash, sha256:kevhash, sha256:reachhash]
+Timestamp: 2025-12-05T00:00:02Z