Add IR remote control (LIRC) with a number-key content mapping

Adds a TCP client for lircd's classic protocol: play/pause/next/prev/
volume/mute map to the same intents every other front-end already
emits, and number keys 0-9 play an assigned album/audiobook from the
start or a podcast show's newest episode, resolved fresh on every
press. The mapping is configured in config.yml and editable from the
frontend: a small "Taste zuweisen" button on the play screen (or the
A+digit keyboard shortcut) opens a 10-key picker to assign whatever is
currently playing.

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

python-backend/tests/test_remote_api.py

@@ -0,0 +1,155 @@
+"""The IR remote's number-key mapping, over the REST API."""
+
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+from pathlib import Path
+
+import httpx2
+import pytest
+
+from musicmouse.config import WebConfig, load_config
+from musicmouse.services.web.service import build_app
+from musicmouse.simulator.harness import Simulation, build_simulation
+from tests.conftest import VALID_CONFIG, write_config
+
+#: A config file with comments, to prove saving does not flatten them.
+COMMENTED = """\
+# The MusicMouse config.
+general:
+  library:
+    root: music
+    cache: .cache
+  serial_port: "/dev/ttyUSB0"
+  alsa_device: simulate
+  min_volume: 0
+  max_volume: 60
+  initial_volume: 40
+
+figures:
+  fuchs:
+    id: "04a1b2c3d4"
+    colors: ["#ff6600", "#ffcc00", "#331100", "wff"]
+  eule:
+    id: "04b2c3d4e5"
+    colors: ["#3355ff", "#66aaff", "#001133", "#ffffff"]
+"""
+
+
+@pytest.fixture
+async def sim(config_dir: Path) -> AsyncIterator[Simulation]:
+    config = load_config(write_config(config_dir, VALID_CONFIG))
+    simulation = await build_simulation(config)
+    try:
+        yield simulation
+    finally:
+        await simulation.aclose()
+
+
+@pytest.fixture
+async def client(sim: Simulation, config_dir: Path) -> AsyncIterator[httpx2.AsyncClient]:
+    path = config_dir / "config.yml"
+    path.write_text(COMMENTED, encoding="utf-8")
+    api, hub = build_app(sim.app, WebConfig(), path)
+    hub.start()
+    transport = httpx2.ASGITransport(app=api)
+    try:
+        async with httpx2.AsyncClient(transport=transport, base_url="http://mouse") as http:
+            yield http
+    finally:
+        hub.stop()
+        await api.state.ha_client.aclose()
+
+
+async def album_id(sim: Simulation, title: str) -> str:
+    return next(a.id for a in sim.app.library.albums if a.title == title)
+
+
+# ------------------------------------------------------------------------------ lirc
+
+
+async def test_lirc_is_a_404_when_unconfigured(client: httpx2.AsyncClient) -> None:
+    assert (await client.get("/api/lirc")).status_code == 404
+
+
+# --------------------------------------------------------------------------- reading
+
+
+async def test_the_mapping_is_empty_by_default(client: httpx2.AsyncClient) -> None:
+    body = (await client.get("/api/remote/mapping")).json()
+    assert body["slots"] == []
+
+
+# --------------------------------------------------------------------------- writing
+
+
+async def test_saving_an_album_slot_round_trips(
+    client: httpx2.AsyncClient, sim: Simulation, config_dir: Path
+) -> None:
+    target = await album_id(sim, "Kinderparty Lieder")
+    response = await client.put(
+        "/api/remote/mapping", json={"slots": {"3": {"target_kind": "album", "target": target}}}
+    )
+    assert response.status_code == 200
+    slots = response.json()["slots"]
+    assert slots == [
+        {"digit": "3", "target_kind": "album", "target": target, "resolved_album_id": target}
+    ]
+
+    text = (config_dir / "config.yml").read_text(encoding="utf-8")
+    assert "# The MusicMouse config." in text  # comments survive
+    reloaded = load_config(config_dir / "config.yml")
+    assert reloaded.remote["3"].target == target
+
+
+async def test_saving_a_series_slot_resolves_to_the_latest_episode(
+    client: httpx2.AsyncClient,
+) -> None:
+    response = await client.put(
+        "/api/remote/mapping",
+        json={"slots": {"7": {"target_kind": "series", "target": "Wissen macht Ah"}}},
+    )
+    assert response.status_code == 200
+    slot = response.json()["slots"][0]
+    assert slot["target_kind"] == "series"
+    assert slot["target"] == "Wissen macht Ah"
+    assert slot["resolved_album_id"] is not None
+
+
+async def test_saving_clears_digits_left_out(
+    client: httpx2.AsyncClient, sim: Simulation
+) -> None:
+    target = await album_id(sim, "Kinderparty Lieder")
+    await client.put(
+        "/api/remote/mapping", json={"slots": {"1": {"target_kind": "album", "target": target}}}
+    )
+    response = await client.put("/api/remote/mapping", json={"slots": {}})
+    assert response.json()["slots"] == []
+
+
+async def test_an_unresolvable_album_target_is_rejected(client: httpx2.AsyncClient) -> None:
+    response = await client.put(
+        "/api/remote/mapping",
+        json={"slots": {"1": {"target_kind": "album", "target": "no-such-album"}}},
+    )
+    assert response.status_code == 422
+    assert "1" in response.json()["detail"]
+
+
+async def test_an_unresolvable_series_target_is_rejected(client: httpx2.AsyncClient) -> None:
+    response = await client.put(
+        "/api/remote/mapping",
+        json={"slots": {"2": {"target_kind": "series", "target": "no such show"}}},
+    )
+    assert response.status_code == 422
+
+
+async def test_a_rejected_save_leaves_the_file_alone(
+    client: httpx2.AsyncClient, config_dir: Path
+) -> None:
+    before = (config_dir / "config.yml").read_text(encoding="utf-8")
+    await client.put(
+        "/api/remote/mapping",
+        json={"slots": {"1": {"target_kind": "album", "target": "no-such-album"}}},
+    )
+    assert (config_dir / "config.yml").read_text(encoding="utf-8") == before