flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/89dbf01df72eb5ebe3b24a86334b12c27d68016a?narHash=sha256-tzYsEzXEVa7op1LTnrLSiPGrcCY6948iD0EcNLWcmzo%3D' (2025-12-29)
  → 'github:NixOS/nixpkgs/64049ca74d63e971b627b5f3178d95642e61cedd?narHash=sha256-yA/CuWyqm%2BAQo2ivGy6PlYrjZBQm7jfbe461%2B4HF2fo%3D' (2026-01-02)

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1767047869,
-        "narHash": "sha256-tzYsEzXEVa7op1LTnrLSiPGrcCY6948iD0EcNLWcmzo=",
+        "lastModified": 1767325753,
+        "narHash": "sha256-yA/CuWyqm+AQo2ivGy6PlYrjZBQm7jfbe461+4HF2fo=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "89dbf01df72eb5ebe3b24a86334b12c27d68016a",
+        "rev": "64049ca74d63e971b627b5f3178d95642e61cedd",
         "type": "github"
       },
       "original": {