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/analyzing-network-flow-data-with-netflow/SKILL.md

@@ -1,16 +1,23 @@
 ---
 name: analyzing-network-flow-data-with-netflow
-description: >-
-  Parse NetFlow v9 and IPFIX records to detect volumetric anomalies, port scanning, data
-  exfiltration, and C2 beaconing patterns. Uses the Python netflow library to decode flow
-  records, builds traffic baselines, and applies statistical analysis to identify flows
-  with abnormal byte counts, connection durations, and periodic timing patterns.
+description: Parse NetFlow v9 and IPFIX records to detect volumetric anomalies, port scanning, data exfiltration, and C2 beaconing
+  patterns. Uses the Python netflow library to decode flow records, builds traffic baselines, and applies statistical analysis
+  to identify flows with abnormal byte counts, connection durations, and periodic timing patterns.
 domain: cybersecurity
 subdomain: network-security
-tags: [analyzing, network, flow, data]
-version: "1.0"
+tags:
+- analyzing
+- network
+- flow
+- data
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.IR-01
+- DE.CM-01
+- ID.AM-03
+- PR.DS-02
 ---