fix(bal): black bar on cancelled invalidation + editable fee follows dates (v0.3.6)

Two GUI fixes bundled together (v0.3.6):

- Fix #10 (black bar): in dialogs.py on_success_phase1, the cancelled
  invalidation branch no longer calls the blocking self.wait(3)+self.close().
  wait() uses time.sleep() and runs in the GUI thread, freezing the UI so the
  'Building Will' dialog could not repaint the area it just resized, leaving a
  black rectangle at the bottom. It now shows 'Aborted' plus the existing
  non-blocking Close button (_add_close_button), consistent with the other
  end-of-flow branches.

- Fix #11 (editable fee): in widgets.py WillSettingsWidget.apply_editable_dates,
  the fee widget (baltx_fees) now follows the same 'Editable dates' setting as
  the locktime/threshold widgets (set_read_only(not editable_dates)) instead of
  being forced read-only. With the setting ticked, dates AND fee are editable
  outside the wizard; unticked, all three are read-only. Default stays OFF.

Version bumped 0.3.5 -> 0.3.6 (manifest.json, __init__.py, plugin_base.py,
VERSION). CHANGELOG: entries #10 and #11. ruff clean; full suite 239 passed.

bal/gui/qt/dialogs.py

@@ -917,9 +917,19 @@ class BalBuildWillDialog(BalDialog):
                 _("Invalidate your old will"), parent=self
             )
             if password is False:
+                # The user cancelled the password prompt for the invalidation.
+                # We must NOT call self.wait(3) here: on_success_phase1 runs in
+                # the GUI thread, so wait()'s time.sleep() would freeze the UI
+                # for several seconds. While frozen the dialog cannot repaint
+                # the area it just resized, leaving a black, undrawn rectangle
+                # at the bottom of the "Building Will" window (the reported bug).
+                #
+                # Instead, mark the invalidation as "Aborted" and offer a
+                # non-blocking "Close" button (the same helper used by the
+                # normal finish path), so the user can read the outcome and
+                # dismiss the dialog when they want, without blocking the GUI.
                 self.msg_set_invalidating(_("Aborted"))
-                self.wait(3)
-                self.close()
+                self._add_close_button()
                 return
             self.thread.add(
                 partial(self.invalidate_task, password, self.bal_window, tx),