fix: sync support private chat content protection

internal/store/private_no_forwards.go

@@ -0,0 +1,15 @@
+package store
+
+import (
+	"context"
+
+	"telesrv/internal/domain"
+)
+
+// PrivateNoForwardsStore keeps the canonical pair state and its service-message
+// transition in one store transaction. It is optional so unrelated lightweight
+// MessageStore test doubles do not need to implement this capability.
+type PrivateNoForwardsStore interface {
+	GetPrivateNoForwards(ctx context.Context, viewerUserID, peerUserID int64) (domain.PrivateNoForwardsState, error)
+	TogglePrivateNoForwards(ctx context.Context, req domain.TogglePrivateNoForwardsRequest) (domain.TogglePrivateNoForwardsResult, error)
+}