refactor: move bottle_state.py to top-level bot_bottle package

Both docker and smolmachines backends use bottle state helpers.
Moving to bot_bottle/ makes the sharing explicit and removes the
cross-backend dependency (smolmachines importing from ..docker).

All callers updated: docker backend, smolmachines backend, cli
modules, and tests.

bot_bottle/cli/start.py

@@ -24,7 +24,7 @@ from ..backend import (
     known_backend_names,
 )
 from ..backend.docker.bottle_plan import DockerBottlePlan
-from ..backend.docker.bottle_state import (
+from ..bottle_state import (
     cleanup_state,
     is_preserved,
     mark_preserved,