fix(ux): replace confirm() with ConfirmModal, fix dark-mode colors, add currency format

- Add reusable ConfirmModal component (themed, Escape key, focus trap)
- Replace all native confirm() calls in Orders, ProductLibrary, Materials, Admin, Billing
- Fix ValidationDialog (Upload.tsx) hardcoded bg-white/text-gray-* → semantic tokens
- Fix NewInvoiceModal (Billing.tsx) hardcoded colors → semantic tokens
- Add formatCurrency (Intl.NumberFormat de-DE/EUR) to NewProductOrder wizard
- Resolves audit issues C1, C3, M3

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

frontend/src/pages/Admin.tsx

@@ -4,6 +4,7 @@ import { toast } from 'sonner'
 import { UserPlus, Trash2, Pencil, ChevronDown, ChevronUp, ChevronRight, Settings, RefreshCw, CheckCircle2, XCircle, Clock, DollarSign, Layers, AlertTriangle, Upload, FileBox, Plus, X, LayoutDashboard } from 'lucide-react'
 import { Link } from 'react-router-dom'
 import api from '../api/client'
+import ConfirmModal from '../components/ConfirmModal'
 import TemplateEditor from '../components/admin/TemplateEditor'
 import PricingTierTable from '../components/admin/PricingTierTable'
 import OutputTypeTable from '../components/admin/OutputTypeTable'
@@ -191,6 +192,7 @@ export default function AdminPage() {
   const [smtpDraft, setSmtpDraft] = useState<Partial<Settings>>({})
   const smtp = { ...settings, ...smtpDraft } as Settings
 
+  const [confirmState, setConfirmState] = useState<{ open: boolean; title: string; message: string; onConfirm: () => void }>({ open: false, title: '', message: '', onConfirm: () => {} })
   const [showTenantDashboardModal, setShowTenantDashboardModal] = useState(false)
   const { data: tenantDefaultWidgets } = useQuery<WidgetConfig[]>({
     queryKey: ['tenant-default-dashboard'],
@@ -276,7 +278,17 @@ export default function AdminPage() {
                 {user.is_active ? 'active' : 'inactive'}
               </span>
               <button
-                onClick={() => { if (confirm('Delete user?')) deleteUserMut.mutate(user.id) }}
+                onClick={() => {
+                  setConfirmState({
+                    open: true,
+                    title: 'Delete User',
+                    message: `Delete user "${user.email}"? This cannot be undone.`,
+                    onConfirm: () => {
+                      deleteUserMut.mutate(user.id)
+                      setConfirmState((s) => ({ ...s, open: false }))
+                    },
+                  })
+                }}
                 className="text-content-muted hover:text-red-500 transition-colors"
                 title="Delete user"
               >
@@ -1440,7 +1452,17 @@ function AssetLibraryPanel() {
                   </button>
                   <button
                     className="btn-danger text-xs"
-                    onClick={() => { if (confirm(`Delete "${lib.name}"?`)) deleteMut.mutate(lib.id) }}
+                    onClick={() => {
+                      setConfirmState({
+                        open: true,
+                        title: 'Delete Asset Library',
+                        message: `Delete "${lib.name}"?`,
+                        onConfirm: () => {
+                          deleteMut.mutate(lib.id)
+                          setConfirmState((s) => ({ ...s, open: false }))
+                        },
+                      })
+                    }}
                   >
                     <Trash2 size={12} />
                   </button>
@@ -1484,6 +1506,14 @@ function AssetLibraryPanel() {
           })}
         </div>
       )}
+
+      <ConfirmModal
+        open={confirmState.open}
+        title={confirmState.title}
+        message={confirmState.message}
+        onConfirm={confirmState.onConfirm}
+        onCancel={() => setConfirmState((s) => ({ ...s, open: false }))}
+      />
     </div>
   )
 }