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>

bot_bottle/backend/docker/capability_apply.py

@@ -30,7 +30,6 @@ semantics open question.
 
 from __future__ import annotations
 
-import os
 import shutil
 import subprocess
 from pathlib import Path
@@ -39,7 +38,6 @@ from ...log import info, warn
 from .bottle_state import (
     mark_preserved,
     per_bottle_dockerfile,
-    per_bottle_dockerfile_path,
     transcript_snapshot_dir,
     write_per_bottle_dockerfile,
 )