[client] Push-based status stream for the Wails UI

Adds a SubscribeStatus gRPC RPC that pushes a fresh FullStatus snapshot
on every peer-recorder state change, replacing the Wails UI's 2-second
Status poll. The daemon's notifier already triggers on Connected /
Disconnected / Connecting / management or signal flip / address
change / peers-list change; we now coalesce those into ticks on a
buffered chan and stream the resulting snapshots over gRPC.

- Status recorder gains SubscribeToStateChanges /
  UnsubscribeFromStateChanges + a non-blocking notifyStateChange that
  drops ticks when a subscriber's 1-slot buffer is full (next snapshot
  the consumer pulls already reflects everything).
- Server.Status handler split: the snapshot composition is shared
  with the new SubscribeStatus stream handler so unary and stream
  paths return identical bytes.
- UI peers service: pollLoop replaced by statusStreamLoop. The local
  name of the existing SubscribeEvents loop is now toastStreamLoop so
  the two streams are easy to tell apart — the underlying RPC name is
  unchanged.
- Tray applyStatus skips the icon refresh when connected/lastStatus
  hasn't changed; rapid SubscribeStatus bursts during health probes
  no longer churn Shell_NotifyIcon or the log.

client/server/server.go

@@ -1101,6 +1101,13 @@ func (s *Server) Status(
 		}
 	}
 
+	return s.buildStatusResponse(msg)
+}
+
+// buildStatusResponse composes a StatusResponse from the current daemon
+// state. Shared between the unary Status RPC and the SubscribeStatus
+// stream so both paths return identical snapshots.
+func (s *Server) buildStatusResponse(msg *proto.StatusRequest) (*proto.StatusResponse, error) {
 	status, err := internal.CtxGetState(s.rootCtx).Status()
 	if err != nil {
 		return nil, err