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/admin/lib/queries/issued-orders.ts

@@ -45,6 +45,7 @@ export interface IssuedOrderDetail extends IssuedOrder {
   delivery_terms: string | null;
   payment_terms: string | null;
   issued_by: string | null;
+  order_text: string | null;
   notes: string | null;
   internal_notes: string | null;
   items: IssuedOrderItem[];

src/admin/pages/IssuedOrderDetail.tsx

@@ -171,6 +171,7 @@ interface OrderForm {
   delivery_terms: string;
   payment_terms: string;
   issued_by: string;
+  order_text: string;
   notes: string;
   internal_notes: string;
   status: string;
@@ -520,6 +521,7 @@ export default function IssuedOrderDetail() {
     delivery_terms: "",
     payment_terms: "",
     issued_by: user?.fullName || "",
+    order_text: "",
     notes: "",
     internal_notes: "",
     status: "draft",
@@ -621,6 +623,7 @@ export default function IssuedOrderDetail() {
       delivery_terms: d.delivery_terms || "",
       payment_terms: d.payment_terms || "",
       issued_by: d.issued_by || "",
+      order_text: d.order_text || "",
       notes: d.notes || "",
       internal_notes: d.internal_notes || "",
       status: d.status,
@@ -779,6 +782,7 @@ export default function IssuedOrderDetail() {
         delivery_terms: form.delivery_terms,
         payment_terms: form.payment_terms,
         issued_by: form.issued_by,
+        order_text: form.order_text || null,
         notes: form.notes,
         internal_notes: form.internal_notes,
         items: items
@@ -1419,6 +1423,16 @@ export default function IssuedOrderDetail() {
 
         {/* Notes & terms */}
         <Card sx={{ mb: 3 }}>
+          <Field label="Text objednávky (na PDF)">
+            <TextField
+              value={form.order_text}
+              disabled={!editable}
+              onChange={(e) =>
+                setForm((prev) => ({ ...prev, order_text: e.target.value }))
+              }
+              placeholder="Objednáváme si u Vás: (ponechte prázdné pro výchozí)"
+            />
+          </Field>
           <Field label="Dodací podmínky">
             <TextField
               value={form.delivery_terms}