Async guard

This should prevent race condition and crashes when when changing modes (locking, unlocking, creating new profile)

clive/__private/ui/forms/create_profile/create_profile_form.py

 from __future__ import annotations
 
-from clive.__private.core.async_guard import AsyncGuard
 from clive.__private.core.profile import Profile
 from clive.__private.ui.forms.create_profile.new_key_alias_form_screen import NewKeyAliasFormScreen
 from clive.__private.ui.forms.create_profile.profile_credentials_form_screen import ProfileCredentialsFormScreen
@@ -10,10 +9,6 @@ from clive.__private.ui.forms.form import ComposeFormResult, Form
 
 
 class CreateProfileForm(Form):
-    def __init__(self) -> None:
-        super().__init__()
-        self._async_guard = AsyncGuard()
-
     async def initialize(self) -> None:
         await self.world.create_new_profile("temp_name")
         self.profile.skip_saving()
@@ -33,24 +28,24 @@ class CreateProfileForm(Form):
         # so this method won't be called
 
         async def impl() -> None:
-            with self._async_guard:
+            with self.app._going_into_unlocked_mode_guard:
                 await self.app.switch_mode("unlock")
                 await self.app.remove_mode("create_profile")
 
-        if self._async_guard.is_available:
+        if self.app._going_into_unlocked_mode_guard.is_available:
             # Has to be done in a separate task to avoid deadlock.
             # More: https://github.com/Textualize/textual/issues/5008
             self.app.run_worker(impl())
 
     async def finish_form(self) -> None:
         async def impl() -> None:
-            with self._async_guard:
+            with self.app._going_into_unlocked_mode_guard:
                 await self.execute_post_actions()
                 self.profile.enable_saving()
                 await self.commands.save_profile()
                 await self.app._switch_mode_into_unlocked()
 
-        if self._async_guard.is_available:
+        if self.app._going_into_unlocked_mode_guard.is_available:
             # Has to be done in a separate task to avoid deadlock.
             # More: https://github.com/Textualize/textual/issues/5008
             self.app.run_worker(impl())