feat(instructions): update security, a11y, and performance to 2025-2026 standards

Security: OWASP 2025 (55 anti-patterns, AI/LLM section, 6 frameworks)
Accessibility: WCAG 2.2 AA (38 anti-patterns, legal context EAA/ADA, 4 frameworks)
Performance: CWV (50 anti-patterns, Next.js 16, Angular 20, modern APIs)

Author: gonzafg2