style: say which lint rules this repo keeps, then keep them

`[tool.ruff]` set a line length and a target version and nothing else, so which
rules ran depended on the installed ruff's defaults — fine while nobody ran it,
not fine for a CI job that can turn a push red because a tool changed its mind.

The set is named explicitly (E, F, I, UP, SIM, B, RUF) with three ignores that
are each a real decision rather than a shrug: B008, because FastAPI's whole
dependency idiom is a call in a default argument; E501, because wrapping prose
is a formatter's business; and RUF001, because the reports and the bot speak
Russian and "ambiguous character" is the wrong complaint about a string the
user is meant to read.

The 73 findings that remained are fixed — mostly `datetime.timezone.utc` →
`datetime.UTC`, `typing.Callable` → `collections.abc.Callable`, import order,
and unused `noqa` markers — plus seven by hand: `contextlib.suppress` for two
try/except/pass pairs, unpacking instead of list concatenation, one negated
return.

`ruff format` is deliberately *not* adopted: it would reformat 51 files, and
some of the layout here is hand-set (the comment tables, the DNS wire-format
structs) in ways a formatter flattens.

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

desktop/kadence_desktop/__main__.py

@@ -38,7 +38,7 @@ def _remote(verb: str) -> int:
     from PyQt6.QtCore import QCoreApplication
     from PyQt6.QtDBus import QDBusConnection, QDBusInterface
 
-    _app = QCoreApplication(sys.argv)  # noqa: F841 - needed for the D-Bus loop
+    _app = QCoreApplication(sys.argv)
     interface = QDBusInterface(
         "org.kadence.Desktop", "/Timer", "org.kadence.Timer", QDBusConnection.sessionBus()
     )