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/9807714d6944a957c2e036f84b0ff8caf9930bc0' (2025-07-08)
• Updated input 'treefmt-nix':
    'github:numtide/treefmt-nix/ac8e6f32e11e9c7f153823abc3ab007f2a65d3e1' (2025-06-26)
  → 'github:numtide/treefmt-nix/c9d477b5d5bd7f26adddd3f96cfd6a904768d4f9' (2025-07-09)
```

flake.lock

@@ -36,11 +36,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1751637120,
-        "narHash": "sha256-xVNy/XopSfIG9c46nRmPaKfH1Gn/56vQ8++xWA8itO4=",
+        "lastModified": 1751984180,
+        "narHash": "sha256-LwWRsENAZJKUdD3SpLluwDmdXY9F45ZEgCb0X+xgOL0=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "5c724ed1388e53cc231ed98330a60eb2f7be4be3",
+        "rev": "9807714d6944a957c2e036f84b0ff8caf9930bc0",
         "type": "github"
       },
       "original": {
@@ -95,11 +95,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1750931469,
-        "narHash": "sha256-0IEdQB1nS+uViQw4k3VGUXntjkDp7aAlqcxdewb/hAc=",
+        "lastModified": 1752055615,
+        "narHash": "sha256-19m7P4O/Aw/6+CzncWMAJu89JaKeMh3aMle1CNQSIwM=",
         "owner": "numtide",
         "repo": "treefmt-nix",
-        "rev": "ac8e6f32e11e9c7f153823abc3ab007f2a65d3e1",
+        "rev": "c9d477b5d5bd7f26adddd3f96cfd6a904768d4f9",
         "type": "github"
       },
       "original": {