feat: add NIST CSF 2.0 nist_csf field to all 754 cybersecurity skills

Mapped every skill to NIST CSF 2.0 subcategory IDs (GV/ID/PR/DE/RS/RC functions)
based on subdomain and content analysis. Restores 11 skills corrupted during
prior rebase, re-enriching with ATLAS, D3FEND, NIST AI RMF, and CSF 2.0 fields.

All 754 skills now carry structured mappings for all 5 security frameworks:
- MITRE ATT&CK (in tags)
- MITRE ATLAS v5.5 (atlas_techniques)
- MITRE D3FEND v1.3 (d3fend_techniques)
- NIST AI RMF 1.0 (nist_ai_rmf)
- NIST CSF 2.0 (nist_csf)

skills/implementing-envelope-encryption-with-aws-kms/SKILL.md

@@ -1,12 +1,23 @@
 ---
 name: implementing-envelope-encryption-with-aws-kms
-description: Envelope encryption is a strategy where data is encrypted with a data encryption key (DEK), and the DEK itself is encrypted with a master key (KEK) managed by AWS KMS. This approach allows encrypting 
+description: Envelope encryption is a strategy where data is encrypted with a data encryption key (DEK), and the DEK itself
+  is encrypted with a master key (KEK) managed by AWS KMS. This approach allows encrypting
 domain: cybersecurity
 subdomain: cryptography
-tags: [cryptography, encryption, aws, kms, envelope-encryption, key-management]
-version: "1.0"
+tags:
+- cryptography
+- encryption
+- aws
+- kms
+- envelope-encryption
+- key-management
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.DS-01
+- PR.DS-02
+- PR.DS-10
 ---
 # Implementing Envelope Encryption with AWS KMS