[FEAT] Add onboarding wizard with visura camerale and CertiSource integration

- New 5-step onboarding wizard (onboarding.html) replacing setup-org.html
- Step 1: Choose data source (Upload Visura / CertiSource / Manual)
- Step 2: PDF upload with AI extraction or CertiSource P.IVA lookup
- Step 3: Verify/complete company data with NIS2 sector mapping
- Step 4: User profile completion
- Step 5: NIS2 classification (Essential/Important) with summary
- OnboardingController with upload-visura, fetch-company, complete endpoints
- VisuraService with Claude AI PDF extraction and ATECO-to-NIS2 mapping
- CertiSource API integration for automatic company data retrieval
- Updated login/register redirects to point to new onboarding wizard

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

public/login.html

@@ -86,7 +86,7 @@
                     if (result.data.organizations && result.data.organizations.length > 0) {
                         window.location.href = 'dashboard.html';
                     } else {
-                        window.location.href = 'setup-org.html';
+                        window.location.href = 'onboarding.html';
                     }
                 } else {
                     errorEl.textContent = result.message || 'Credenziali non valide.';