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/__tests__/drafts-deferred-numbering.test.ts

@@ -51,6 +51,8 @@ describe("issued-order drafts — deferred numbering", () => {
   it("a draft has no number and does NOT consume the sequence", async () => {
     const before = (await previewIssuedOrderNumber()).number;
     const draft = await createIssuedOrder({}); // defaults to draft
+    if ("error" in draft)
+      throw new Error(`createIssuedOrder failed: ${draft.error}`);
     issuedOrderIds.push(draft.id);
     expect(draft.status).toBe("draft");
     expect(draft.po_number).toBeNull();
@@ -62,6 +64,8 @@ describe("issued-order drafts — deferred numbering", () => {
   it("finalizing a draft (draft -> sent) assigns the next sequence number", async () => {
     const expected = (await previewIssuedOrderNumber()).number;
     const draft = await createIssuedOrder({});
+    if ("error" in draft)
+      throw new Error(`createIssuedOrder failed: ${draft.error}`);
     issuedOrderIds.push(draft.id);
 
     const res = await updateIssuedOrder(draft.id, { status: "sent" });
@@ -77,6 +81,8 @@ describe("issued-order drafts — deferred numbering", () => {
 
   it("finalizing is idempotent — re-finalizing does not re-number", async () => {
     const draft = await createIssuedOrder({});
+    if ("error" in draft)
+      throw new Error(`createIssuedOrder failed: ${draft.error}`);
     issuedOrderIds.push(draft.id);
 
     await updateIssuedOrder(draft.id, { status: "sent" });
@@ -104,6 +110,8 @@ describe("issued-order drafts — deferred numbering", () => {
   it("two drafts coexist with null numbers (no unique violation)", async () => {
     const a = await createIssuedOrder({});
     const b = await createIssuedOrder({});
+    if ("error" in a) throw new Error(`createIssuedOrder failed: ${a.error}`);
+    if ("error" in b) throw new Error(`createIssuedOrder failed: ${b.error}`);
     issuedOrderIds.push(a.id, b.id);
     expect(a.po_number).toBeNull();
     expect(b.po_number).toBeNull();
@@ -112,6 +120,8 @@ describe("issued-order drafts — deferred numbering", () => {
   it("deleting a draft releases nothing (no number was consumed)", async () => {
     const before = (await previewIssuedOrderNumber()).number;
     const draft = await createIssuedOrder({});
+    if ("error" in draft)
+      throw new Error(`createIssuedOrder failed: ${draft.error}`);
     await deleteIssuedOrder(draft.id);
     const after = (await previewIssuedOrderNumber()).number;
     expect(after).toBe(before);