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/unit/test_capability_apply.py

@@ -13,7 +13,8 @@ import unittest
 from pathlib import Path
 
 from bot_bottle import supervise
-from bot_bottle.backend.docker import bottle_state, capability_apply
+from bot_bottle import bottle_state
+from bot_bottle.backend.docker import capability_apply
 from bot_bottle.backend.docker.capability_apply import (
     CapabilityApplyError,
     apply_capability_change,