feat(foreground): foreground process sensors + translation key migration

Adds Home Assistant entities for the foreground-process feature shipped
in the media server, plus migrates existing display entities to use HA
translation keys (strings.json / translations/*) so per-language UI text
flows through the standard locale mechanism.

Foreground entities (all share one HA "Foreground" device linked to the
hub via via_device):
- sensor.foreground_process — process name as state + full payload
  (pid, exec path, window title, fullscreen flag, monitor, geometry,
  is_browser, browser_page_title, browser_url, error) as attributes
- sensor.window_title, sensor.pid, sensor.foreground_monitor,
  sensor.process_started (TIMESTAMP device class)
- binary_sensor.fullscreen, binary_sensor.minimized

Data flow:
- ForegroundCoordinator polls GET /api/foreground every 5s (HTTP fallback)
- media_player's WebSocket receiver forwards `foreground` /
  `foreground_update` push frames into the coordinator via
  apply_websocket_snapshot, so sensors update in near-real-time when WS
  is connected and fall back to polling otherwise

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

custom_components/remote_media_player/binary_sensor.py

@@ -15,6 +15,8 @@ from homeassistant.helpers.update_coordinator import CoordinatorEntity
 from .const import DOMAIN
 from .display_coordinator import DisplayCoordinator
 from .display_device import display_device_info
+from .foreground import FOREGROUND_BINARY_SENSORS
+from .foreground_coordinator import ForegroundCoordinator
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -24,22 +26,33 @@ async def async_setup_entry(
     entry: ConfigEntry,
     async_add_entities: AddEntitiesCallback,
 ) -> None:
-    """Set up per-display binary sensor entities."""
-    coordinator: DisplayCoordinator = hass.data[DOMAIN][entry.entry_id][
-        "display_coordinator"
-    ]
-
-    if not coordinator.data:
-        return
+    """Set up display + foreground binary sensor entities."""
+    store = hass.data[DOMAIN][entry.entry_id]
+    display_coordinator: DisplayCoordinator = store["display_coordinator"]
+    foreground_coordinator: ForegroundCoordinator | None = store.get(
+        "foreground_coordinator"
+    )
 
     entities: list[Any] = []
-    for monitor in coordinator.data.values():
-        entities.append(DisplayPrimaryBinarySensor(coordinator, entry, monitor))
-        entities.append(DisplayPowerControlBinarySensor(coordinator, entry, monitor))
+    if display_coordinator.data:
+        for monitor in display_coordinator.data.values():
+            entities.append(
+                DisplayPrimaryBinarySensor(display_coordinator, entry, monitor)
+            )
+            entities.append(
+                DisplayPowerControlBinarySensor(display_coordinator, entry, monitor)
+            )
+
+    if foreground_coordinator is not None:
+        entities.extend(
+            cls(foreground_coordinator, entry) for cls in FOREGROUND_BINARY_SENSORS
+        )
 
     if entities:
         async_add_entities(entities)
-        _LOGGER.info("Added %d display binary sensor entities", len(entities))
+        _LOGGER.info(
+            "Added %d binary sensor entities (display + foreground)", len(entities)
+        )
 
 
 class _DisplayBinarySensorBase(
@@ -70,7 +83,7 @@ class _DisplayBinarySensorBase(
 class DisplayPrimaryBinarySensor(_DisplayBinarySensorBase):
     """Indicates whether the display is the OS primary monitor."""
 
-    _attr_name = "Primary display"
+    _attr_translation_key = "primary_display"
     _attr_icon = "mdi:monitor-star"
 
     def __init__(
@@ -90,7 +103,7 @@ class DisplayPrimaryBinarySensor(_DisplayBinarySensorBase):
 class DisplayPowerControlBinarySensor(_DisplayBinarySensorBase):
     """Indicates whether DDC/CI power control is available for this display."""
 
-    _attr_name = "Power control supported"
+    _attr_translation_key = "power_control_supported"
     _attr_icon = "mdi:power-plug"
 
     def __init__(