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/backend/smolmachines/resolve_plan.py

@@ -17,7 +17,7 @@ from pathlib import Path
 
 from ...agent_provider import PROVIDER_TEMPLATES, agent_provision_plan, get_provider
 from ...backend import BottleSpec
-from ...backend.docker.bottle_state import (
+from ...bottle_state import (
     BottleMetadata,
     agent_state_dir,
     bottle_identity,