feat: add will-executor edit dialog on double-click with sync button (↻)

- WillExecutorListWidget: double-click/Enter opens edit dialog
- WillExecutorWidget.add() accepts edit_key param for edit mode:
  pre-populates URL, Info, Base Fee, Address fields
- Sync button (↻) pings executor URL via TaskThread and populates
  fields; updates executor status in list in edit mode (200/KO)
- Loading indicator (⟳) during async ping
- QMessageBox with dialog as parent for sync errors
- Focus returns to URL field after sync error
- 'Add another' button only in add mode, no longer default (OK is default)
- Removed Promo Code field
- Heir dialog: 'Add another' no longer default (matches new pattern)

bal/gui/qt/window.py

@@ -218,7 +218,6 @@ class BalWindow:
             d.accept()
 
         new_heir_button.clicked.connect(new_heir)
-        new_heir_button.setDefault(True)
 
         grid.addWidget(QLabel(_("Name")), 1, 0)
         grid.addWidget(heir_name, 1, 1)