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.

tests/integration/test_capability_apply.py

@@ -31,7 +31,7 @@ import unittest
 from pathlib import Path
 
 from bot_bottle import supervise
-from bot_bottle.backend.docker import bottle_state
+from bot_bottle import bottle_state
 from bot_bottle.backend.docker.capability_apply import apply_capability_change
 from bot_bottle.backend.docker.network import (
     network_create_egress,

tests/integration/test_sandbox_escape.py

@@ -29,7 +29,7 @@ import unittest
 from pathlib import Path
 
 from bot_bottle.backend import BottleSpec, get_bottle_backend
-from bot_bottle.backend.docker.bottle_state import cleanup_state
+from bot_bottle.bottle_state import cleanup_state
 from bot_bottle.manifest import Manifest
 from tests._docker import skip_unless_docker