Closes#82
`@self.tree.interaction_check` in `setup_hook` called the coroutine as
a decorator factory instead of overriding it — producing an unawaited
coroutine warning and leaving maintenance mode as a no-op.
Replace with `MaintenanceAwareTree(discord.app_commands.CommandTree)` that
overrides `interaction_check`, and pass `tree_cls=MaintenanceAwareTree`
to `super().__init__`. Remove the now-obsolete decorator block from
`setup_hook`.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
