feat(issued-orders): editable PDF heading 'Text objednavky (na PDF)' (order_text)

New nullable issued_orders.order_text column (migration applied to dev+test). The heading above the PDF items table is now editable per order, mirroring invoices' billing_text: empty falls back to the default, which is now 'Objednavame si u Vas:' per user wording. Field sits above Dodaci podminky in the detail form; persisted via create + update strFields (both schemas - the invoices Update-schema gap is not repeated). Tests: persistence round-trip incl. null-clears, PDF custom heading + default fallback.

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

src/__tests__/issued-orders.test.ts

@@ -170,6 +170,23 @@ describe("createIssuedOrder", () => {
     const res = await createIssuedOrder({ supplier_id: 99999999 });
     expect("error" in res && res.error).toBe("supplier_not_found");
   });
+
+  it("persists order_text on create, updates and clears it on update", async () => {
+    const order = await mkIssued({ order_text: "Objednáváme dle smlouvy:" });
+    let row = await prisma.issued_orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(row!.order_text).toBe("Objednáváme dle smlouvy:");
+
+    await updateIssuedOrder(order.id, { order_text: "Jiný text:" });
+    row = await prisma.issued_orders.findUnique({ where: { id: order.id } });
+    expect(row!.order_text).toBe("Jiný text:");
+
+    // null clears back to the PDF default.
+    await updateIssuedOrder(order.id, { order_text: null });
+    row = await prisma.issued_orders.findUnique({ where: { id: order.id } });
+    expect(row!.order_text).toBeNull();
+  });
 });
 
 describe("updateIssuedOrder status transitions", () => {
@@ -507,6 +524,29 @@ describe("renderIssuedOrderHtml", () => {
     expect(html).not.toContain("alert(1)");
   });
 
+  it("renders the custom order_text heading when set, default when not", () => {
+    const custom = renderIssuedOrderHtml(
+      { ...order, order_text: "Objednáváme dle nabídky č. 123:" },
+      items,
+      null,
+      null,
+      "cs",
+      issuer,
+    );
+    expect(custom).toContain("Objednáváme dle nabídky č. 123:");
+    expect(custom).not.toContain("Objednáváme si u Vás:");
+
+    const fallback = renderIssuedOrderHtml(
+      order,
+      items,
+      null,
+      null,
+      "cs",
+      issuer,
+    );
+    expect(fallback).toContain("Objednáváme si u Vás:");
+  });
+
   it("with VAT: keeps the VAT columns and the DPH cell holds ONLY the line VAT", () => {
     const html = renderIssuedOrderHtml(order, items, null, null, "cs", issuer);
     expect(html).toContain("%DPH");