flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/d6973081434f88088e5321f83ebafe9a1167c367?narHash=sha256-cuNapx/uQeCgeuhUhdck3JKbgpsml259sjUQnWM7zW8%3D' (2025-01-02)
  → 'github:NixOS/nixpkgs/18dd725c29603f582cf1900e0d25f9f1063dbf11?narHash=sha256-awS2zRgF4uTwrOKwwiJcByDzDOdo3Q1rPZbiHQg/N38%3D' (2025-04-13)

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1735821806,
+        "lastModified": 1744536153,
-        "narHash": "sha256-cuNapx/uQeCgeuhUhdck3JKbgpsml259sjUQnWM7zW8=",
+        "narHash": "sha256-awS2zRgF4uTwrOKwwiJcByDzDOdo3Q1rPZbiHQg/N38=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d6973081434f88088e5321f83ebafe9a1167c367",
+        "rev": "18dd725c29603f582cf1900e0d25f9f1063dbf11",
         "type": "github"
       },
       "original": {