fix(qt): auto-close Plugins manager, read-only field styling, RLock-safe heirs persistence

GUI / plugin lifecycle:
- Auto-close Electrum's native 'Electrum Plugins' manager dialog after the
  BAL plugin is hot-enabled. Electrum 4.7.x no longer calls the old init_qt
  hook, so the close is now triggered from the create_status_bar, init_menubar
  and load_wallet hooks (fired when reload_windows() recreates the window).
- Robust dialog matching (isinstance / class name / localized window title) to
  cope with zipimport module-identity mismatches.
- Robust dismissal of the modal dialog (reject()/done()/close()) with a retry
  schedule [400, 800, 1500] ms; if it still cannot be closed, fall back to
  bringing it to the front (showNormal/raise_/activateWindow) so it never
  lingers hidden in the background. Counting only visible top-levels avoids
  treating an already-closed dialog as still open.

Read-only field styling:
- Paint the locked Delivery time / Check Alive date editors and the mining-fee
  spinbox with a light-grey background (#f0f0f0) so the user can see at a glance
  that they are not editable outside the 'Build your will' wizard; the styling
  is cleared when the fields are made editable again.

Pickle/RLock crash on 'Build will':
- heirs.save() now sanitises the heirs mapping via _json_safe() before handing
  it to json_db.put(), which deep-copies the value. A live runtime object
  (holding a threading.RLock) slipping into an heir value previously raised
  'TypeError: cannot pickle _thread.RLock object' and aborted the task; such
  values are now coerced to str and logged with their path.
- init_heirs_to_locktime() coerces the locktime to a plain serializable scalar.
- log_error() now accepts both a sys.exc_info() triple and a single exception
  instance, fixing the secondary 'TypeError object is not subscriptable' that
  masked the real error.

bal/gui/qt/dialogs.py

@@ -381,7 +381,10 @@ class BalWizardLocktimeAndFeeWidget(BalWizardWidget):
         widget = QWidget()
         layout = QVBoxLayout(widget)
 
-        layout.addWidget(WillSettingsWidget(self.bal_window, self, "v"))
+        # The wizard ("Build your will") is the ONLY place the delivery time,
+        # check alive and fee can be edited, so it is the only read_only=False.
+        layout.addWidget(WillSettingsWidget(self.bal_window, self, "v",
+                                            read_only=False))
         spacer_widget = QWidget()
         spacer_widget.setSizePolicy(
             QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding