User Manager: undo/redo user add and delete on a device

Uses LiveComponentCommand, so undoing a delete puts the user back on
the device with its exact cred, perm and prov.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app_state.py

@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.150"
+VERSION = "0.0.0.151"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True

user_service_view.py

@@ -449,7 +449,10 @@ class _UserDialog:
             ET.SubElement(elem, "prop", name=name, val=val)
 
         if app_state.live_mode:
+            index = len(list(self._service_comp))
             self._service_comp.append(elem)
+            undo.push(sax_file.LiveComponentCommand(
+                self._service_comp, index, elem, present=True, label="add user"))
             app_state.mark_dirty()
             app_state.set_status(f"User '{username}' added to device.")
             return
@@ -643,12 +646,24 @@ class UserServicePanel:
             return
 
         if app_state.live_mode:
+            # Read before it goes: once deleted, the device has nothing left to read back.
+            snapshot = live_hooks.read_subtree(user_elem)
+            unreadable = live_hooks.last_error if snapshot is None else ""
             if not live_hooks.live_delete_component(user_elem):
                 live_hooks.warn_failure("Delete User", f"User '{name}' was not deleted from the device")
                 return
+            index = list(self.comp).index(user_elem)
             self.comp.remove(user_elem)
             app_state.mark_dirty()
+            if snapshot is not None:
+                undo.push(sax_file.LiveComponentCommand(
+                    self.comp, index, user_elem, present=False, snapshot=snapshot,
+                    label="delete user"))
                 app_state.set_status(f"User '{name}' deleted from device.")
+            else:
+                app_state.set_status(
+                    f"User '{name}' was deleted from the device, but this delete cannot be "
+                    f"undone: {unreadable}", warn=True)
             self._after_change()
             return