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-zero-knowledge-proof-for-authentication/SKILL.md

@@ -1,12 +1,22 @@
 ---
 name: implementing-zero-knowledge-proof-for-authentication
-description: Zero-Knowledge Proofs (ZKPs) allow a prover to demonstrate knowledge of a secret (such as a password or private key) without revealing the secret itself. This skill implements the Schnorr identificati
+description: Zero-Knowledge Proofs (ZKPs) allow a prover to demonstrate knowledge of a secret (such as a password or private
+  key) without revealing the secret itself. This skill implements the Schnorr identificati
 domain: cybersecurity
 subdomain: cryptography
-tags: [cryptography, zero-knowledge-proof, authentication, privacy, zkp]
-version: "1.0"
+tags:
+- cryptography
+- zero-knowledge-proof
+- authentication
+- privacy
+- zkp
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.DS-01
+- PR.DS-02
+- PR.DS-10
 ---
 # Implementing Zero-Knowledge Proof for Authentication