style: ruff's own fixes, mechanically applied

`ruff check .` had gone unrun long enough to report 568 errors, which is the
same as having no linter: the next real finding would have been invisible in the
noise. This is the 521 it fixes by itself, in 173 files, and nothing else — the
98 it cannot fix are the next commit.

What actually changed: import sorting (225), imports nobody used (87, none of
them a re-export — no `__init__.py` is touched, which was the one way this could
have broken an import elsewhere), `datetime.timezone.utc` to `datetime.UTC` (69)
and `asyncio.TimeoutError` to `TimeoutError` (18), both plain aliases on the 3.12
this project requires, `Optional[X]` to `X | None` (24), and f-strings with
nothing to interpolate (19).

Checked rather than assumed: every module in the three packages still imports,
and the suite is 2893 passed — the same count, test for test, as the merge
before it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/packages/meshbay-node/tests/test_transfer_settings.py b/packages/meshbay-node/tests/test_transfer_settings.py
index bcfa6a8..a2c7fd9 100644
--- a/packages/meshbay-node/tests/test_transfer_settings.py
+++ b/packages/meshbay-node/tests/test_transfer_settings.py
@@ -19,10 +19,12 @@ shape of the bug this whole branch started from (`webrtc._stream_sem`).
 """
 
 import pytest
-
 from meshbay_node.roster import Roster
 from meshbay_node.transfers import (
-    DEFAULT_MAX_PER_MEMBER, DOWNLOAD, UPLOAD, TransferSlots,
+    DEFAULT_MAX_PER_MEMBER,
+    DOWNLOAD,
+    UPLOAD,
+    TransferSlots,
 )