[FEAT] L4 AI Cross-Analysis — analisi aggregata multi-org per consulenti

- CrossAnalysisController.php: analyze/history/portfolio (k-anonymity min 2 org)
- AIService::crossOrgAnalysis(): aggregazione 9 dimensioni, zero PII nel prompt
- cross-analysis.html: chat UI purple theme, 3 tab, quick questions, portfolio stats
- index.php: routing /api/cross-analysis/{analyze,history,portfolio}
- common.js: link "AI Cross-Analysis" in sidebar sezione Gestione
- docs/AI_LEVELS_SCHEMA.md: schema architetturale L1-L5 con matrice privacy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/js/common.js

@@ -199,6 +199,7 @@ function loadSidebar() {
                 { name: 'Supply Chain', href: 'supply-chain.html',   icon: iconLink(),              i18nKey: 'nav.supply_chain' },
                 { name: 'Segnalazioni', href: 'whistleblowing.html', icon: `<svg viewBox="0 0 20 20" fill="currentColor"><path fill-rule="evenodd" d="M5 9V7a5 5 0 0110 0v2a2 2 0 012 2v5a2 2 0 01-2 2H5a2 2 0 01-2-2v-5a2 2 0 012-2zm8-2v2H7V7a3 3 0 016 0z" clip-rule="evenodd"/></svg>` },
                 { name: 'Normative',    href: 'normative.html',      icon: `<svg viewBox="0 0 20 20" fill="currentColor"><path fill-rule="evenodd" d="M4 4a2 2 0 012-2h4.586A2 2 0 0112 2.586L15.414 6A2 2 0 0116 7.414V16a2 2 0 01-2 2H6a2 2 0 01-2-2V4zm2 6a1 1 0 011-1h6a1 1 0 110 2H7a1 1 0 01-1-1zm1 3a1 1 0 100 2h6a1 1 0 100-2H7z" clip-rule="evenodd"/></svg>` },
+                { name: 'AI Cross-Analysis', href: 'cross-analysis.html', icon: `<svg viewBox="0 0 20 20" fill="currentColor"><path d="M13 6a3 3 0 11-6 0 3 3 0 016 0zM18 8a2 2 0 11-4 0 2 2 0 014 0zM14 15a4 4 0 00-8 0v3h8v-3zM6 8a2 2 0 11-4 0 2 2 0 014 0zM16 18v-3a5.972 5.972 0 00-.75-2.906A3.005 3.005 0 0119 15v3h-3zM4.75 12.094A5.973 5.973 0 004 15v3H1v-3a3 3 0 013.75-2.906z"/></svg>` },
             ]
         },
         {