fix(plan): drop the redundant 'Zrušit' button in the category-management modal

The Správa kategorií modal footer had two buttons that both just close it (Zrušit + Zavřít). Added an opt-in hideCancel prop to the kit Modal (default false → every other modal unchanged) and set it on PlanCategoriesModal, leaving only 'Zavřít'. Verified: footer shows only Zavřít; close/Escape/backdrop intact.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/ui/Modal.tsx

@@ -18,6 +18,8 @@ export interface ModalProps {
   submitDisabled?: boolean;
   submitText?: string;
   cancelText?: string;
+  /** Hide the secondary cancel button (e.g. modals whose only action closes). */
+  hideCancel?: boolean;
   maxWidth?: "xs" | "sm" | "md" | "lg";
 }
 
@@ -33,6 +35,7 @@ export default function Modal({
   submitDisabled = false,
   submitText = "Uložit",
   cancelText = "Zrušit",
+  hideCancel = false,
   maxWidth = "sm",
 }: ModalProps) {
   useDialogScrollLock(isOpen);
@@ -73,9 +76,11 @@ export default function Modal({
       </DialogTitle>
       <DialogContent>{children}</DialogContent>
       <DialogActions sx={{ px: 3, pb: 2 }}>
-        <MuiButton onClick={onClose} color="inherit" disabled={shown.loading}>
-          {cancelText}
-        </MuiButton>
+        {!hideCancel && (
+          <MuiButton onClick={onClose} color="inherit" disabled={shown.loading}>
+            {cancelText}
+          </MuiButton>
+        )}
         <MuiButton
           onClick={onSubmit}
           variant="contained"