[FEAT] UI: guida online, landing EN, mobile-conversion, ai-assistant, bug-reporter + help/i18n

- public/guida.html, index-en.html, service-continuity.html
- public/js/ai-assistant.js, bug-reporter.js (FAB supporto)
- public/mobile-conversion.css/js
- index.html, common.js, help.js, risks.html: aggiornamenti UI/help

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

public/js/common.js

@@ -214,6 +214,7 @@ function loadSidebar() {
         {
             label: 'Sistema', i18nKey: 'nav.system',
             items: [
+                { name: 'Guida all\'uso', href: 'guida.html', icon: `<svg viewBox="0 0 20 20" fill="currentColor"><path fill-rule="evenodd" d="M18 10a8 8 0 11-16 0 8 8 0 0116 0zm-7-4a1 1 0 11-2 0 1 1 0 012 0zM9 9a1 1 0 000 2v3a1 1 0 001 1h1a1 1 0 100-2v-3a1 1 0 00-1-1H9z" clip-rule="evenodd"/></svg>` },
                 { name: 'Impostazioni', href: 'settings.html',     icon: iconCog(),             i18nKey: 'nav.settings' },
                 { name: 'Architettura', href: 'architecture.html', icon: iconCubeTransparent() },
                 { name: 'Simulazione Demo', href: 'simulate.html', icon: `<svg viewBox="0 0 20 20" fill="currentColor"><path fill-rule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zM9.555 7.168A1 1 0 008 8v4a1 1 0 001.555.832l3-2a1 1 0 000-1.664l-3-2z" clip-rule="evenodd"/></svg>` },