🚧 Add broker status page

backend/app/schemas.py

@@ -230,6 +230,43 @@ class ConfigPreviewOut(BaseModel):
     warnings: list[str]
 
 
+class BrokerStatusOut(BaseModel):
+    """$SYS snapshot for the dashboard (spec sections 33, 55).
+
+    Every metric is None until the first $SYS publish arrives (the
+    broker publishes on sys_interval, 10 s in the bootstrap config);
+    `available` says whether ANY $SYS message has been ingested.
+    """
+
+    available: bool
+    last_update: datetime | None
+    version: str | None = None
+    uptime: str | None = None
+    build_timestamp: str | None = None
+    clients_connected: int | None = None
+    clients_disconnected: int | None = None
+    clients_maximum: int | None = None
+    clients_total: int | None = None
+    clients_expired: int | None = None
+    messages_received: int | None = None
+    messages_sent: int | None = None
+    messages_stored: int | None = None
+    messages_dropped: int | None = None
+    publish_received: int | None = None
+    publish_sent: int | None = None
+    publish_dropped: int | None = None
+    bytes_received: int | None = None
+    bytes_sent: int | None = None
+    subscriptions_count: int | None = None
+    retained_count: int | None = None
+    load_messages_received_1min: float | None = None
+    load_messages_sent_1min: float | None = None
+    load_publish_received_1min: float | None = None
+    load_publish_sent_1min: float | None = None
+    load_bytes_received_1min: float | None = None
+    load_bytes_sent_1min: float | None = None
+
+
 class DeployRequest(BaseModel):
     comment: str | None = None