docs: update CLAUDE.md with Italian rule, error workflow, and full data model

Added Italian communication requirement, error-first workflow (report then wait),
and missing Prisma models: ProductVariant, PasswordResetToken, Page/PageSection,
SiteSettings, AuditLog. Added app/coverage/ to .gitignore.

.gitignore

@@ -6,11 +6,15 @@
 # Node
 app/node_modules/
 node_modules/
+test/node_modules
 
 # Next.js build output
 app/.next/
 app/out/
 
+# Test coverage report
+app/coverage/
+
 # Prisma generated client (rebuilt on npm install)
 app/node_modules/.prisma/