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/configuring-oauth2-authorization-flow/SKILL.md

@@ -1,12 +1,26 @@
 ---
 name: configuring-oauth2-authorization-flow
-description: Configure secure OAuth 2.0 authorization flows including Authorization Code with PKCE, Client Credentials, and Device Authorization Grant. This skill covers flow selection, PKCE implementation, token 
+description: Configure secure OAuth 2.0 authorization flows including Authorization Code with PKCE, Client Credentials, and
+  Device Authorization Grant. This skill covers flow selection, PKCE implementation, token
 domain: cybersecurity
 subdomain: identity-access-management
-tags: [iam, identity, access-control, authentication, authorization, oauth2, oidc, pkce]
-version: "1.0"
+tags:
+- iam
+- identity
+- access-control
+- authentication
+- authorization
+- oauth2
+- oidc
+- pkce
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.AA-01
+- PR.AA-02
+- PR.AA-05
+- PR.AA-06
 ---
 # Configuring OAuth 2.0 Authorization Flow