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/window.py

@@ -432,11 +432,26 @@ class BalWindow:
         self.bal_plugin.WILL_SETTINGS.set(self.will_settings)
 
     def init_heirs_to_locktime(self, multiverse=False):
-        #pass
-        for heir in self.heirs:
-            h = self.heirs[heir]
-            if not multiverse:
-                self.heirs[heir] = [h[0], h[1], self.will_settings["locktime"]]
+        if multiverse:
+            return
+        # Coerce the locktime to a plain serializable scalar: will_settings is
+        # read from Electrum's config and a non-primitive value here would end
+        # up inside the heirs dict and break json_db persistence (this was one
+        # path to the "cannot pickle '_thread.RLock' object" error).
+        locktime = self.will_settings["locktime"]
+        if not isinstance(locktime, (int, float, str)):
+            locktime = str(locktime)
+        # Iterate over a snapshot of the keys: assigning to self.heirs[...]
+        # triggers Heirs.__setitem__ -> save(), which mutates the mapping while
+        # we iterate it.  Building the new values first and applying them after
+        # the loop avoids "dict changed size during iteration" and the repeated
+        # save() on every heir.
+        updates = {
+            heir: [self.heirs[heir][0], self.heirs[heir][1], locktime]
+            for heir in list(self.heirs)
+        }
+        for heir, value in updates.items():
+            self.heirs[heir] = value
 
     def init_class_variables(self):
         if not self.heirs: