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_http_users_me.py

@@ -1,5 +1,4 @@
 """Tests for PUT /api/0/users/me logic."""
-import pytest
 from hbd.server import users as users_mod
 
 
@@ -87,7 +86,6 @@ def test_put_users_me_notification_channels(tmp_path):
 
 def test_visible_channels_excludes_private_from_others():
     """Private channels owned by another user must not appear in the visible set."""
-    from hbd.server import settings as settings_mod
 
     config = {
         "notification_channels": {
@@ -105,7 +103,7 @@ def test_visible_channels_excludes_private_from_others():
             self.admin = admin
 
     alice = FakeUser("alice")
-    bob   = FakeUser("bob")
+    bob = FakeUser("bob")
     admin = FakeUser("admin", admin=True)
 
     # Simulate _visible_channels_for_user logic (mirrors http.py implementation)
@@ -119,5 +117,5 @@ def test_visible_channels_excludes_private_from_others():
         }
 
     assert visible(alice) == {"public_ch", "alice_priv"}
-    assert visible(bob)   == {"public_ch", "bob_priv"}
+    assert visible(bob) == {"public_ch", "bob_priv"}
     assert visible(admin) == {"public_ch", "alice_priv", "bob_priv"}