flake.lock: Update

Flake lock file updates:

```
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/a684c58d46ebbede49f280b653b9e56100aa3877' (2025-06-27)
  → 'github:nixos/nixpkgs/50ab793786d9de88ee30ec4e4c24fb4236fc2674' (2025-06-30)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/30e2e2857ba47844aa71991daa6ed1fc678bcbb7' (2025-06-27)
  → 'github:nixos/nixpkgs/5c724ed1388e53cc231ed98330a60eb2f7be4be3' (2025-07-04)
```

flake.lock

@@ -36,11 +36,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1751271578,
-        "narHash": "sha256-P/SQmKDu06x8yv7i0s8bvnnuJYkxVGBWLWHaU+tt4YY=",
+        "lastModified": 1751637120,
+        "narHash": "sha256-xVNy/XopSfIG9c46nRmPaKfH1Gn/56vQ8++xWA8itO4=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "3016b4b15d13f3089db8a41ef937b13a9e33a8df",
+        "rev": "5c724ed1388e53cc231ed98330a60eb2f7be4be3",
         "type": "github"
       },
       "original": {