feat(issued-orders): counterparty is now a supplier (dodavatel), not a customer

Issued orders are purchase orders WE send - they must pick from suppliers
(sklad_suppliers), not from customers. Per user decision customer_id was
REPLACED (not kept alongside): migration drops issued_orders.customer_id and
adds supplier_id FK -> sklad_suppliers (existing rows lose their counterparty
- the feature is days old; re-point them in the UI).

- service: input/filters/search (suppliers.name + ico)/enrichment/detail all
  supplier-based; create validates the supplier inside the transaction and
  update before write -> Czech 400 'Dodavatel nenalezen' instead of P2003 500;
  detail returns a minimal supplier field set (no internal notes leak)
- routes: supplier_id on list + stats; new GET /issued-orders/suppliers
  lookup (orders.view/create/edit guard - orders users lack warehouse.manage
  which guards the warehouse suppliers CRUD), active suppliers only,
  name+id ordering
- PDF: Dodavatel block now renders the supplier (name, newline-split address,
  IC/DIC), layout and both language label sets unchanged
- frontend: new SupplierPicker kit component (CustomerPicker untouched),
  IssuedOrderDetail/IssuedOrders switched to supplier_id/supplier_name; the
  picker keeps a fallback option for orders whose supplier was later
  deactivated; WarehouseSuppliers CRUD now also invalidates issued-orders so
  the picker can't go stale
- tests: issued-orders suite switched to supplier fixtures + new coverage
  (lookup shape + 403, nonexistent supplier 400, PDF supplier block)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/admin/pages/WarehouseSuppliers.tsx

@@ -137,7 +137,9 @@ export default function WarehouseSuppliers() {
     url: () =>
       editingSupplier ? `${API_BASE}/${editingSupplier.id}` : API_BASE,
     method: () => (editingSupplier ? "PUT" : "POST"),
-    invalidate: ["warehouse"],
+    // issued-orders included: the PO form's supplier picker caches under
+    // ["issued-orders","suppliers"] and must see supplier CRUD immediately.
+    invalidate: ["warehouse", "issued-orders"],
     onSuccess: (data) => {
       setShowModal(false);
       alert.success(data?.message || "Dodavatel byl uložen");
@@ -147,7 +149,9 @@ export default function WarehouseSuppliers() {
   const deleteMutation = useApiMutation<number, { message?: string }>({
     url: (id) => `${API_BASE}/${id}`,
     method: () => "DELETE",
-    invalidate: ["warehouse"],
+    // issued-orders included: the PO form's supplier picker caches under
+    // ["issued-orders","suppliers"] and must see supplier CRUD immediately.
+    invalidate: ["warehouse", "issued-orders"],
     onSuccess: (data) => {
       setDeactivateConfirm({ show: false, supplier: null });
       alert.success(data?.message || "Dodavatel byl smazán");
@@ -163,7 +167,9 @@ export default function WarehouseSuppliers() {
   >({
     url: ({ id }) => `${API_BASE}/${id}`,
     method: () => "PUT",
-    invalidate: ["warehouse"],
+    // issued-orders included: the PO form's supplier picker caches under
+    // ["issued-orders","suppliers"] and must see supplier CRUD immediately.
+    invalidate: ["warehouse", "issued-orders"],
   });
 
   if (!hasPermission("warehouse.manage")) return <Forbidden />;