flake.lock: Update

Flake lock file updates:

```
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/cdd2ef009676ac92b715ff26630164bb88fec4e0' (2025-03-13)
  → 'github:nixos/nixpkgs/7105ae3957700a9646cc4b766f5815b23ed0c682' (2025-03-20)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/6607cf789e541e7873d40d3a8f7815ea92204f32' (2025-03-13)
  → 'github:nixos/nixpkgs/a84ebe20c6bc2ecbcfb000a50776219f48d134cc' (2025-03-19)
```

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1742268799,
-        "narHash": "sha256-IhnK4LhkBlf14/F8THvUy3xi/TxSQkp9hikfDZRD4Ic=",
+        "lastModified": 1742512142,
+        "narHash": "sha256-8XfURTDxOm6+33swQJu/hx6xw1Tznl8vJJN5HwVqckg=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "da044451c6a70518db5b730fe277b70f494188f1",
+        "rev": "7105ae3957700a9646cc4b766f5815b23ed0c682",
         "type": "github"
       },
       "original": {
@@ -36,11 +36,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1742288794,
-        "narHash": "sha256-Txwa5uO+qpQXrNG4eumPSD+hHzzYi/CdaM80M9XRLCo=",
+        "lastModified": 1742422364,
+        "narHash": "sha256-mNqIplmEohk5jRkqYqG19GA8MbQ/D4gQSK0Mu4LvfRQ=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b6eaf97c6960d97350c584de1b6dcff03c9daf42",
+        "rev": "a84ebe20c6bc2ecbcfb000a50776219f48d134cc",
         "type": "github"
       },
       "original": {