feat: server telemetry, update entity, sync-clock controls

- Server device exposing CPU/RAM/GPU/temperature/battery sensors via
  /api/v1/system/performance, plus last-restart timestamp (cached with
  jitter threshold so the recorder doesn't see poll wobble) and version.
- Update entity backed by /api/v1/system/update — installs via
  /apply, hides the install button when the server reports
  can_auto_update=false.
- Sync-clock entities: reset button, speed number, running switch, and
  the event listener now refreshes on entity_changed events too.
- Bump manifest to 0.4.0.

custom_components/ledgrab/button.py

@@ -25,12 +25,16 @@ async def async_setup_entry(
     data = hass.data[DOMAIN][entry.entry_id]
     coordinator: LedGrabCoordinator = data[DATA_COORDINATOR]
 
-    entities = []
+    entities: list[ButtonEntity] = []
     if coordinator.data:
         for preset in coordinator.data.get("scene_presets", []):
             entities.append(
                 SceneActivateButton(coordinator, preset, entry.entry_id)
             )
+        for clock in coordinator.data.get("sync_clocks", []):
+            entities.append(
+                SyncClockResetButton(coordinator, clock["id"], entry.entry_id)
+            )
 
     async_add_entities(entities)
 
@@ -72,3 +76,38 @@ class SceneActivateButton(CoordinatorEntity, ButtonEntity):
     async def async_press(self) -> None:
         """Activate the scene preset."""
         await self.coordinator.activate_scene(self._preset_id)
+
+
+class SyncClockResetButton(CoordinatorEntity, ButtonEntity):
+    """Button that resets a sync clock to t=0 (linked animations restart)."""
+
+    _attr_has_entity_name = True
+    _attr_icon = "mdi:restart"
+
+    def __init__(
+        self,
+        coordinator: LedGrabCoordinator,
+        clock_id: str,
+        entry_id: str,
+    ) -> None:
+        super().__init__(coordinator)
+        self._clock_id = clock_id
+        self._entry_id = entry_id
+        self._attr_unique_id = f"{clock_id}_reset"
+        self._attr_translation_key = "sync_clock_reset"
+
+    @property
+    def device_info(self) -> dict[str, Any]:
+        return {"identifiers": {(DOMAIN, self._clock_id)}}
+
+    @property
+    def available(self) -> bool:
+        if not self.coordinator.data:
+            return False
+        return any(
+            c.get("id") == self._clock_id
+            for c in self.coordinator.data.get("sync_clocks", [])
+        )
+
+    async def async_press(self) -> None:
+        await self.coordinator.reset_sync_clock(self._clock_id)