Add "Mein Zimmer" room-control page (Home Assistant, proxied through the backend)

Implements the room-control page from the design mockup: a scenes row above cards
for shutters, color lamps, and brightness-only lamps, all driven by a new
`general.ha` config section (server URL, token, ordered device/scene lists).

The backend proxies every Home Assistant call server-side (GET/POST /api/ha/...)
rather than the browser calling Home Assistant directly, so the long-lived token
never leaves the LAN device and Home Assistant's own CORS settings don't need to
know about musicmouse at all. Card kind (shutter/color/brightness-only) is
inferred at runtime from what Home Assistant reports about each entity, not
configured explicitly.

Also stops tracking python-backend/config.yml, which had drifted into the repo
despite its own header saying it shouldn't be - it now carries real credentials
locally and needs to stay untracked.

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

python-backend/tests/test_config.py

@@ -52,6 +52,75 @@ def test_web_section_is_optional(config_dir: Path) -> None:
     assert config.general.web.static_dir == (config_dir / "dist").resolve()
 
 
+def test_ha_section_is_optional(config_dir: Path) -> None:
+    assert load_config(write_config(config_dir, VALID_CONFIG)).general.ha is None
+
+
+def test_ha_device_and_scene_name_is_optional(config_dir: Path) -> None:
+    data = _config(
+        ha={
+            "url": "http://homeassistant.local:8123",
+            "token": "abc123",
+            "devices": [{"entity_id": "light.a"}],
+            "scenes": [{"entity_id": "scene.a"}],
+        }
+    )
+    config = load_config(write_config(config_dir, data))
+    assert config.general.ha is not None
+    assert config.general.ha.devices[0].name is None
+    assert config.general.ha.scenes[0].name is None
+
+
+def test_ha_devices_and_scenes_preserve_config_order(config_dir: Path) -> None:
+    data = _config(
+        ha={
+            "url": "http://homeassistant.local:8123",
+            "token": "abc123",
+            "devices": [
+                {"entity_id": "cover.rollo"},
+                {"entity_id": "light.deckenlampe"},
+                {"entity_id": "light.beyond_links"},
+            ],
+            "scenes": [
+                {"entity_id": "scene.aufwachen"},
+                {"entity_id": "scene.lesen"},
+            ],
+        }
+    )
+    config = load_config(write_config(config_dir, data))
+    ha = config.general.ha
+    assert ha is not None
+    assert [d.entity_id for d in ha.devices] == [
+        "cover.rollo",
+        "light.deckenlampe",
+        "light.beyond_links",
+    ]
+    assert [s.entity_id for s in ha.scenes] == ["scene.aufwachen", "scene.lesen"]
+
+
+def test_ha_requires_devices_or_scenes(config_dir: Path) -> None:
+    message = _error(
+        config_dir,
+        _config(ha={"url": "http://ha", "token": "abc", "devices": [], "scenes": []}),
+    )
+    assert "configure at least one device or scene" in message
+
+
+def test_ha_rejects_unknown_key_on_a_device(config_dir: Path) -> None:
+    message = _error(
+        config_dir,
+        _config(
+            ha={
+                "url": "http://ha",
+                "token": "abc",
+                "devices": [{"entity_id": "light.a", "kind": "beyond"}],
+                "scenes": [],
+            }
+        ),
+    )
+    assert "unknown option" in message
+
+
 # --------------------------------------------------------------------- error paths