style: format all code to PEP8 (flake8 clean)

Reformat every module with autopep8 and hand-tune the remaining long
lines so that `flake8` passes with default settings (max line length
79). No behavior changes: long f-strings, messages, QSS/Textual CSS
rules and argument lists are only wrapped or split, an unused import
and an unused local are dropped, and dbus-next D-Bus signature
annotations carry targeted `# noqa` comments.

player.py

@@ -67,7 +67,8 @@ class MusicPlayer:
         return command + [url]
 
     async def set_volume(self, volume: int) -> None:
-        """Меняет громкость; ffplay/mpv не умеют на лету, поэтому перезапускаем."""
+        """Меняет громкость; ffplay/mpv не умеют на лету, поэтому
+        перезапускаем."""
         self.volume = max(0, min(100, int(volume)))
         if self.url and self.is_playing():
             position = self.elapsed()
@@ -145,7 +146,12 @@ class MusicPlayer:
         if not self.proc:
             return 0.0
         now = self.paused_at if self.paused else time.monotonic()
-        return max(0.0, self.offset + now - self.started_at - self.paused_total)
+        return max(
+            0.0,
+            self.offset +
+            now -
+            self.started_at -
+            self.paused_total)
 
     async def seek(self, delta: float, duration: float) -> None:
         """Seek by delta seconds. Restarts ffplay at the new position."""