[Backport release-26.05] radicle-node: mark insecure (#566484)

pkgs/by-name/ra/radicle-node/package.nix

@@ -173,5 +173,9 @@ rustPlatform.buildRustPackage (finalAttrs: {
     platforms = lib.platforms.unix;
     teams = [ lib.teams.radicle ];
     mainProgram = "rad";
+    knownVulnerabilities = [
+      # https://radicle.dev/2026/09/23/disclosure-of-vulnerability-in-network-protocol
+      "Private repositories are insecure: traffic between nodes is not encrypted and not authenticated."
+    ];
   };
 })