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_cli_start_settle.py

@@ -9,7 +9,7 @@ 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.cli import start as start_mod