Target the Python that Raspberry Pi OS ships

Requiring 3.13 meant the device needed an interpreter the distribution does not
have, which is what dragged uv in, and uv then had to be matched to the Pi's
32-bit userland by hand and to build Pillow from source because no armv7 wheel
exists for a 3.13 ABI. Dropping to 3.11 removes all of that: apt provides the
interpreter and piwheels has prebuilt armhf wheels for the native dependencies.

The 3.13-only syntax was shallow - PEP 695 throughout, which converts back
mechanically:

  type X = Y               ->  X: TypeAlias = Y
  type Handler[E: Event]   ->  E = TypeVar("E", bound=Event) plus a plain alias,
                               which is generic anyway because it carries a TypeVar
  def f[T: Bound](...)     ->  a module-level TypeVar

Also drop the one @override (3.12, and static-only), and stop the lirc test
harness calling Server.close_clients(), which is 3.13: the scripted handler now
releases its connection when asked, which is what that call was there to force.

Verified on 3.11.14 - 485 passed, mypy strict clean - and still 496 passed on
the 3.14 dev venv, which additionally has the analysis extra.

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

python-backend/musicmouse/__main__.py

@@ -19,7 +19,7 @@ import logging
 import sys
 from collections.abc import Awaitable, Callable, Coroutine
 from pathlib import Path
-from typing import Any
+from typing import Any, TypeVar
 
 import httpx2
 
@@ -324,7 +324,10 @@ def _build_app(
     return app
 
 
-def _service_of_type[T: Service](services: list[Service], kind: type[T]) -> T | None:
+T = TypeVar("T", bound=Service)
+
+
+def _service_of_type(services: list[Service], kind: type[T]) -> T | None:
     return next((s for s in services if isinstance(s, kind)), None)