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-zscaler-private-access-for-ztna/SKILL.md

@@ -1,15 +1,28 @@
 ---
 name: configuring-zscaler-private-access-for-ztna
-description: >
-  Configuring Zscaler Private Access (ZPA) to replace traditional VPN with zero trust
-  network access by deploying App Connectors, defining application segments, configuring
-  access policies based on user identity and device posture, and integrating with IdPs.
+description: 'Configuring Zscaler Private Access (ZPA) to replace traditional VPN with zero trust network access by deploying
+  App Connectors, defining application segments, configuring access policies based on user identity and device posture, and
+  integrating with IdPs.
+
+  '
 domain: cybersecurity
 subdomain: zero-trust-architecture
-tags: [zscaler, zpa, ztna, zero-trust, app-connector, access-policy, sase]
-version: "1.0"
+tags:
+- zscaler
+- zpa
+- ztna
+- zero-trust
+- app-connector
+- access-policy
+- sase
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.AA-01
+- PR.AA-05
+- PR.IR-01
+- GV.PO-01
 ---
 
 # Configuring Zscaler Private Access for ZTNA