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/strings.json

@@ -44,7 +44,7 @@
         "name": "Processing"
       },
       "sync_clock_running": {
-        "name": "Running"
+        "name": "Active"
       }
     },
     "sensor": {
@@ -65,6 +65,36 @@
       },
       "sync_clock_elapsed": {
         "name": "Elapsed Time"
+      },
+      "server_cpu_percent": {
+        "name": "CPU Usage"
+      },
+      "server_ram_percent": {
+        "name": "RAM Usage"
+      },
+      "server_app_cpu_percent": {
+        "name": "App CPU Usage"
+      },
+      "server_app_ram": {
+        "name": "App Memory"
+      },
+      "server_gpu_utilization": {
+        "name": "GPU Usage"
+      },
+      "server_gpu_temp": {
+        "name": "GPU Temperature"
+      },
+      "server_cpu_temp": {
+        "name": "CPU Temperature"
+      },
+      "server_battery": {
+        "name": "Battery"
+      },
+      "server_last_restart": {
+        "name": "Last Restart"
+      },
+      "server_version": {
+        "name": "Server Version"
       }
     },
     "number": {
@@ -105,6 +135,11 @@
           "nearest": "Nearest"
         }
       }
+    },
+    "update": {
+      "server_update": {
+        "name": "Server Update"
+      }
     }
   },
   "services": {