flake.lock: Update

Flake lock file updates:

```
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/cdd2ef009676ac92b715ff26630164bb88fec4e0' (2025-03-13)
  → 'github:nixos/nixpkgs/da044451c6a70518db5b730fe277b70f494188f1' (2025-03-18)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/6607cf789e541e7873d40d3a8f7815ea92204f32' (2025-03-13)
  → 'github:nixos/nixpkgs/b6eaf97c6960d97350c584de1b6dcff03c9daf42' (2025-03-18)
```

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1741862977,
-        "narHash": "sha256-prZ0M8vE/ghRGGZcflvxCu40ObKaB+ikn74/xQoNrGQ=",
+        "lastModified": 1742268799,
+        "narHash": "sha256-IhnK4LhkBlf14/F8THvUy3xi/TxSQkp9hikfDZRD4Ic=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "cdd2ef009676ac92b715ff26630164bb88fec4e0",
+        "rev": "da044451c6a70518db5b730fe277b70f494188f1",
         "type": "github"
       },
       "original": {
@@ -36,11 +36,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1741851582,
-        "narHash": "sha256-cPfs8qMccim2RBgtKGF+x9IBCduRvd/N5F4nYpU0TVE=",
+        "lastModified": 1742288794,
+        "narHash": "sha256-Txwa5uO+qpQXrNG4eumPSD+hHzzYi/CdaM80M9XRLCo=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "6607cf789e541e7873d40d3a8f7815ea92204f32",
+        "rev": "b6eaf97c6960d97350c584de1b6dcff03c9daf42",
         "type": "github"
       },
       "original": {