feat: Add metadata fields to security checks (layer, phase, use case, framework)

[vivekmittal514]

Summary

Each security check currently has severity, service, and status. Adding structured categorization fields would improve filtering, reporting, and compliance mapping — and unlock the work in issues for NIST AI RMF mapping and multi-tab report structure.

Proposed Fields

Field	Example values
layer	Infrastructure, Data, Model, Application, Agent
phase	Build, Deploy, Runtime, Monitor
use_case	RAG, Fine-tuning, Inference, Agent
framework	Well-Architected GenAI Lens, OWASP LLM Top 10, NIST AI RMF

Files Likely Touched

• All assessor files in aiml-security-assessment/functions/security/*/ — add fields to each check result dict
• HTML report template — add new filter dropdowns for these fields
• docs/SECURITY_CHECKS.md and docs/AIMLSecurityAssessment-MappingsTable.csv — add new columns

Acceptance Criteria

• All existing checks have values for all four new fields
• Report UI exposes filters for each new field
• CSV export includes the new columns
• Developer guide documents the expected field values and allowed vocabulary

Notes

This is a foundational issue — NIST AI RMF / ISO 42001 mapping and the multi-tab report structure both depend on these fields being present. Recommended to tackle this first.