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/number.py

@@ -32,6 +32,9 @@ async def async_setup_entry(
             if source.get("source_type") == "api_input":
                 entities.append(ApiInputTimeout(coordinator, source, entry.entry_id))
 
+        for clock in coordinator.data.get("sync_clocks") or []:
+            entities.append(SyncClockSpeed(coordinator, clock["id"], entry.entry_id))
+
     if coordinator.data and "targets" in coordinator.data:
         devices = coordinator.data.get("devices") or {}
 
@@ -300,3 +303,60 @@ class ApiInputTimeout(CoordinatorEntity, NumberEntity):
             if source.get("id") == self._source_id:
                 return source
         return None
+
+
+# --- Sync clock number entities ---
+
+
+class SyncClockSpeed(CoordinatorEntity, NumberEntity):
+    """Speed multiplier for a sync clock (server range 0.1–10.0).
+
+    Hot-applied — running animations linked to the clock change pace
+    immediately without resetting their position.
+    """
+
+    _attr_has_entity_name = True
+    _attr_native_min_value = 0.1
+    _attr_native_max_value = 10.0
+    _attr_native_step = 0.1
+    _attr_mode = NumberMode.SLIDER
+    _attr_icon = "mdi:speedometer"
+
+    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}_speed"
+        self._attr_translation_key = "sync_clock_speed"
+
+    @property
+    def device_info(self) -> dict[str, Any]:
+        return {"identifiers": {(DOMAIN, self._clock_id)}}
+
+    @property
+    def native_value(self) -> float | None:
+        clock = self._get_clock()
+        if not clock:
+            return None
+        speed = clock.get("speed")
+        return float(speed) if speed is not None else None
+
+    @property
+    def available(self) -> bool:
+        return self._get_clock() is not None
+
+    async def async_set_native_value(self, value: float) -> None:
+        await self.coordinator.update_sync_clock(self._clock_id, speed=round(value, 2))
+
+    def _get_clock(self) -> dict[str, Any] | None:
+        if not self.coordinator.data:
+            return None
+        for clock in self.coordinator.data.get("sync_clocks", []):
+            if clock.get("id") == self._clock_id:
+                return clock
+        return None