Add yarr: Rust MCP server for media automation fleets (Sonarr, Radarr, Prowlarr, Jellyfin, SABnzbd, qBittorrent, Plex)

Replaces the Node.js-based mcp-arr-server and jellyfin-mcp backends
in the gateway with a single Rust binary that covers both *arr and
Jellyfin. Rust binaries work through the gateway's stdio spawn
(where Node.js ones fail with 401).

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1781577229,
-        "narHash": "sha256-lrp67w8AulE9Ks53n27I45ADSzbOCn4H+CNW1Ck8B+8=",
+        "lastModified": 1786599213,
+        "narHash": "sha256-yNJd40f11EzXBjSByCB7IPpeFFAdeoSKKM67dGkfFoU=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "567a49d1913ce81ac6e9582e3553dd90a955875f",
+        "rev": "0e251e24a4f24e036a084b6b4b2d2491af4167f4",
         "type": "github"
       },
       "original": {