refactor: fix unused imports, long lines, and type issues

Remove 35+ unused imports across 20+ files (W0611). Wrap 19 lines
to fit under 100 character limit (C0301). Add type casts and
annotations in egress_addon_core.py to resolve pyright errors
caused by JSON parsing of untyped objects.

Key changes:
- Remove unused imports (abstractmethod, mock utilities, etc)
- Split long lines at logical breaks (method calls, error messages)
- Add typing.cast() for proper type inference in JSON parsing
- Explicit type annotations for dict/list accesses

Results:
- Pylint rating: 8.73/10
- egress_addon_core.py: 0 pyright errors (was 15)
- All W0611 and C0301 issues fixed

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

tests/unit/test_cli_start_selector.py

@@ -9,10 +9,8 @@ All actual launch work is stubbed so no container is created.
 from __future__ import annotations
 
 import os
-import sys
-import types
 import unittest
-from unittest.mock import MagicMock, patch, call
+from unittest.mock import MagicMock, patch
 
 import bot_bottle.cli.start as start_mod
 import bot_bottle.cli.tui as tui_mod