style: apply ruff auto-fixes across codebase

- Fix import sorting (isort) across all engine modules
- Fix SIM105 try-except-pass patterns (contextlib.suppress)
- Fix nested with statements in tests
- Fix unused loop variables

Run 'uv run pytest' to verify tests still pass.

engine/ntfy.py

@@ -13,8 +13,8 @@ Reusable by any visualizer:
 """
 
 import json
-import time
 import threading
+import time
 import urllib.request
 from urllib.parse import urlparse, parse_qs, urlencode, urlunparse