feat(my-customers): flatten orders into per-device cards

- split orders by device_name into FlattenedDevice entries
- strip device prefixes from product and module names
- render one DeviceCard per Kasse in the customer accordion
- add targeted upgrade URL with orderId, customer_id, device_id
- wizard starts at step 3 in upgrade mode with locked customer
- mark existing licensed modules as read-only with badge

shop/app/my-customers/page.tsx

@@ -1,8 +1,8 @@
 export const dynamic = 'force-dynamic';
 import { redirect } from 'next/navigation'
 import Link from 'next/link'
-import { getPartnerCustomersWithOrders } from '@/lib/actions/queries'
-import type { EndCustomerWithOrders } from '@/lib/types'
+import { getPartnerCustomersWithDevices } from '@/lib/actions/queries'
+import type { EndCustomerWithDevices } from '@/lib/types'
 import { ArrowLeft, Building2, Plus, AlertTriangle } from 'lucide-react'
 import { Button } from '@/components/ui/button'
 import { createClient } from '@/lib/supabase/server'
@@ -13,10 +13,10 @@ export default async function MyCustomersPage() {
   const { data: { user } } = await supabase.auth.getUser()
   if (!user) redirect('/auth/login')
 
-  let customers: EndCustomerWithOrders[] = []
+  let customers: EndCustomerWithDevices[] = []
   let fetchError: string | null = null
   try {
-    customers = await getPartnerCustomersWithOrders()
+    customers = await getPartnerCustomersWithDevices()
   } catch (err: any) {
     console.error("Error loading partner customers with orders:", err)
     fetchError = err.message || "Es gab ein Problem beim Laden Ihrer Kunden und Kassen."