style: clear whitespace, unused-import and blank-line lint

Strip trailing whitespace, drop unused imports/variables/global statements,
split multi-imports, fix E3xx/E1xx spacing and E712 comparisons. No behaviour
change; only E501 long lines remain in flake8.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/test_oauth.py

@@ -37,7 +37,6 @@ def reset_users_dict():
     users_mod.users = original
 
 
-
 def test_make_state_returns_unique_tokens():
     s1 = oauth.make_state()
     s2 = oauth.make_state()
@@ -124,7 +123,6 @@ def test_provision_oauth_user_survives_config_reload():
     assert "oauthonly" in users_mod.users
 
 
-
 # ---------------------------------------------------------------------------
 # Integration-style tests: callback logic chain
 # ---------------------------------------------------------------------------