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/performing-second-order-sql-injection/SKILL.md

@@ -1,12 +1,25 @@
 ---
 name: performing-second-order-sql-injection
-description: Detect and exploit second-order SQL injection vulnerabilities where malicious input is stored in a database and later executed in an unsafe SQL query during a different application operation.
+description: Detect and exploit second-order SQL injection vulnerabilities where malicious input is stored in a database and
+  later executed in an unsafe SQL query during a different application operation.
 domain: cybersecurity
 subdomain: web-application-security
-tags: [second-order-sqli, stored-sql-injection, sql-injection, database-security, web-security, blind-injection, persistent-sqli]
-version: "1.0"
+tags:
+- second-order-sqli
+- stored-sql-injection
+- sql-injection
+- database-security
+- web-security
+- blind-injection
+- persistent-sqli
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.PS-01
+- ID.RA-01
+- PR.DS-10
+- DE.CM-01
 ---
 
 # Performing Second-Order SQL Injection