update: bump 6 MCP packages + nixpkgs flake

- flake.lock: nixpkgs 2026-05-31 → 2026-06-16
- zotero-mcp: v0.2.2 → v0.5.0
- duckduckgo-mcp-server: 0.1.1-unstable → v0.4.0
- kindly-web-search-mcp-server: bump to latest commit + add trafilatura dep
- sabnzbd-mcp: pin to specific commit instead of refs/heads/main
- jellyfin-mcp: v2026.318.7 → v2026.604.2 (remove go.mod patch)
- nextcloud-mcp-server: v0.89.0 → v0.121.3

n8n-mcp, mcp-arr-server, pdf-reader-mcp held back:
upstream npm packages require @modelcontextprotocol/sdk versions
not yet published to npm registry

packages/sabnzbd-mcp/package.nix

@@ -23,7 +23,7 @@ stdenv.mkDerivation {
   src = fetchFromGitHub {
     owner = "jmagar";
     repo = "sabnzbd-mcp";
-    rev = "refs/heads/main";
+    rev = "9d691ed70b72397fddec03ca4ec68c81b30c79c3";
     hash = "sha256-1sEnHH40cDVT5oiZD2Xywl7S9vJThii/ce+6r+XmpSw=";
   };