refactor(rules): group focused security rules

shared/rules/security/references/data.md

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+# Database and data security
+
+* Use parameterized queries or ORM parameter binding; never concatenate untrusted input into SQL.
+* Use least-privilege database accounts and protect connection strings.
+* Scope tenant-owned queries explicitly and prevent cross-tenant cache, logging, and diagnostic leakage.
+* Collect and retain only necessary sensitive data; encrypt it in transit and at rest where appropriate.
+* Avoid raw database errors and use transactions where integrity requires atomicity.